CN112835244B - Nonlinear polarization control system and method for circular birefringent optical fiber Mach-Zehnder interference system - Google Patents

Nonlinear polarization control system and method for circular birefringent optical fiber Mach-Zehnder interference system Download PDF

Info

Publication number
CN112835244B
CN112835244B CN202110009326.0A CN202110009326A CN112835244B CN 112835244 B CN112835244 B CN 112835244B CN 202110009326 A CN202110009326 A CN 202110009326A CN 112835244 B CN112835244 B CN 112835244B
Authority
CN
China
Prior art keywords
optical fiber
polarization
circular
fiber
mach
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202110009326.0A
Other languages
Chinese (zh)
Other versions
CN112835244A (en
Inventor
王春华
宁金星
方捻
高瑞娟
李力
谷祥
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Shanghai for Science and Technology
Original Assignee
University of Shanghai for Science and Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University of Shanghai for Science and Technology filed Critical University of Shanghai for Science and Technology
Priority to CN202110009326.0A priority Critical patent/CN112835244B/en
Publication of CN112835244A publication Critical patent/CN112835244A/en
Application granted granted Critical
Publication of CN112835244B publication Critical patent/CN112835244B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/3511—Self-focusing or self-trapping of light; Light-induced birefringence; Induced optical Kerr-effect
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/3515—All-optical modulation, gating, switching, e.g. control of a light beam by another light beam
    • G02F1/3517—All-optical modulation, gating, switching, e.g. control of a light beam by another light beam using an interferometer

Landscapes

  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

The invention discloses a Mach-Zehnder interference structure (MZI) of a circular birefringent optical fiber based on nonlinear polarization control. The invention constructs the circular birefringent fiber MZI by utilizing the nonlinear polarization traction mechanism that the polarization state of the signal light is always pulled to the polarization state of the incident pump light which is transmitted oppositely in the stimulated Brillouin scattering effect of the circular birefringent fiber, and increases the reverse transmission pump light to enable the signal light and the signal light to generate the nonlinear stimulated Brillouin scattering effect in two circular birefringent fiber interference arms of the MZI. Because the polarization states of the incident pump light entering the two interference arms from the output end in opposite directions are the same, the polarization states of the two paths of signal light reaching the output end through the two interference arms are both pulled to the polarization state of the incident pump light, the output light polarization states in the MZI are kept consistent, and the problem of polarization interference noise caused by random stress birefringence introduced by internal and external factors of an optical fiber of the interference arm in a general optical fiber MZI is solved.

Description

Nonlinear polarization control system and method for circular birefringent optical fiber Mach-Zehnder interference system
Technical Field
The invention relates to the field of optical information processing, in particular to a nonlinear polarization control system and method of a circular birefringent optical fiber Mach-Zehnder interference system.
Background
Random polarization perturbations in optical fibers are a major problem that plagues interferometric fiber systems. The problems of polarization phase noise and polarization fading of interference signals caused by polarization disturbance appear in the optical sensing system. In a sensing system of a single-mode optical fiber or a polarization maintaining optical fiber Mach-Zehnder interference structure, especially in a long-distance optical fiber Mach-Zehnder interference system, due to anisotropy of a geometric structure of an optical fiber caused in a drawing process, external stress borne by the optical fiber interference system in laying and installation and bending torsion stress generated by bending and coiling of the optical fiber can introduce random birefringence in the optical fiber, and the stress birefringence changes along with the change of environmental temperature, so that the random disturbance of the polarization states of transmission light of two interference arms in the optical fiber Mach-Zehnder interference system is caused, the random change of the output polarization states of the two interference arms causes output interference fading, namely polarization noise of interference light intensity.
In the existing optical fiber Mach-Zehnder interference system, the solution method of the polarization noise mainly comprises the following steps: the polarization diversity receiving method, the polarization state modulation method, the polarization state feedback control method and the full polarization maintaining method. The polarization diversity receiving method adopts multi-polarization state polarization detection receiving at a signal receiving end, and the receiving scheme is complex; the polarization state modulation method mainly carries out polarization disturbance modulation or orthogonal polarization state modulation on the polarization state of the signal light, and carries out weighted average on the influence of the polarization state; the polarization feedback control method monitors, feeds back and controls the light polarization states of the two interference arms, thereby reducing the polarization noise of the interference system; the full polarization maintaining method is a scheme which is applied more at present, a Mach-Zehnder interference system is constructed by adopting polarization maintaining optical fibers, the input optical polarization state is strictly controlled to be injected in a linear polarization mode along the main shaft direction of the optical fibers, and the thin-diameter optical fibers or mechanical protection measures are strictly selected, so that the stress action of the two interference arm optical fibers from the outside is reduced, and the polarization state of signal light in the optical fibers is always kept in the main shaft direction. However, since the core size of the optical fiber is relatively fixed (5-10 μm) and the cladding of the optical fiber is much larger than the core of the optical fiber, even if a small diameter optical fiber is used, the birefringence of the optical fiber due to the bending stress of the optical fiber is reduced but not eliminated. Excessive mechanical protection not only increases the environmental adaptation difficulty of system operation, but also weakens the system sensitivity of the optical fiber as the sensing arm. Therefore, the search for an effective polarization control method in the fiber optic interferometric system has been a problem faced by the interferometric fiber optic sensing system.
Therefore, those skilled in the art have been devoted to developing a nonlinear polarization interference noise-resistant method of an interference system constructed by a circular birefringent optical fiber Mach-Zehnder.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the technical problem to be solved by the present invention is how to attenuate the interference polarization noise of signal light caused by the random stress birefringence of the optical fiber in various sensing, measuring, etc. systems using the optical fiber Mach-Zehnder interference structure.
In order to achieve the above object, the present invention provides a circular birefringent optical fiber Mach-Zehnder interference system based on nonlinear polarization control, which comprises a first isolator, a first polarization controller, a circular birefringent optical fiber Mach-Zehnder interference structure, a second polarization controller, an optical amplifier and a second isolator;
the output end of the first isolator is connected with one end of a first polarization controller, and the other end of the first polarization controller is connected with one side of a circular birefringent optical fiber Mach-Zehnder interference structure; the input end of the second isolator is connected with the output end of the optical amplifier, the output end of the second isolator is connected with one end of a second polarization controller, and the other end of the second polarization controller is connected with the other side of the circular birefringent optical fiber Mach-Zehnder interference structure; frequency v p The pump light enters from the reverse port of the circular birefringent optical fiber Mach-Zehnder interference structure after passing through the optical amplifier and the second isolator, and the frequency is v s After passing through the first isolator, the signal light enters from a positive port of the circular birefringent optical fiber Mach-Zehnder interference structure, in two interference arms of the circular birefringent optical fiber Mach-Zehnder interference structure, a stimulated Brillouin scattering effect occurs between the pump light propagating in the positive direction and the signal light propagating in the reverse direction, and the signal light polarization state propagating in the positive direction in the two interference arms is pulled to the position of the incident pump light polarization state; the circular birefringent optical fiber Mach-Zehnder interference structure comprises a first circular birefringent optical fiber coupler, a first circular birefringent optical fiber, a second circular birefringent optical fiber and a second circular birefringent optical fiber coupler, wherein one port on one side of the first circular birefringent optical fiber coupler is connected with a first polarization controller, and two ends on the other side of the first circular birefringent optical fiber coupler are respectively connected with the first circular birefringent optical fiber and the second circular birefringent optical fiber; other ports of the first circular birefringent fiber and the second circular birefringent fiber are connected with two ports on the same side of the second circular refractive fiber coupler; and one port on the other side of the second circular birefringent fiber coupler is connected with the second polarization controller.
Furthermore, the first circular birefringent optical fiber coupler has a splitting ratio of K 1 ∶(1-K 1 ) (wherein 0. ltoreq. K 1 ≦ 1), a 2x2 coupling device in which the polarization state of the coupling region remains unchanged or changes synchronously, including but not limited to a circularly birefringent fiber coupler.
The second circular birefringent fiber coupler has a splitting ratio of K 2 ∶(1-K 2 ) (wherein 0. ltoreq. K 2 ≦ 1), 2x2 coupler with constant or synchronous change in polarization state of the coupling regionAn article, including but not limited to a circularly birefringent fiber coupler.
Further, the first circularly birefringent optical fiber has a length L 1 The second circularly birefringent optical fiber has a length L 2 Wherein (L) 1 、L 2 > 0). Furthermore, the optical fiber of the circular birefringent optical coupler and the optical fiber of the interference arm are the same optical fiber, so as to ensure that the SBS frequency shift of the tail fiber of the splitter is the same as that of the optical fiber of the interference arm, and the circular birefringent optical fiber can be a round birefringent optical fiber or a circular birefringent optical fiber processed by other processes.
The invention also provides a nonlinear polarization control method of the circular birefringent optical fiber Mach-Zehnder interference system based on nonlinear polarization control, which comprises the following steps:
(a) will have a frequency v s Signal light of frequency v p The pump light is respectively input into the circular birefringence optical fiber Mach-Zehnder interference structure through a forward port and a reverse port of the circular birefringence optical fiber Mach-Zehnder interference system based on nonlinear polarization control;
(b) the input pump light and the signal light respectively propagate in opposite directions in the two interference arms, and a stimulated Brillouin scattering effect occurs between the forward propagating signal light and the backward propagating pump light in the two interference arms. The polarization states of the forward propagating signal lights in the two interference arms are all pulled by the polarization of the backward transmitting pump lights with the same incident polarization state, so that the output polarization states of the output signal lights in the two interference arms of the Mach-Zehnder interference structure are all pulled to the position of the polarization state of the incident pump lights.
Further, the frequency v of the pump light in the step (a) p And the frequency v of the signal light s Satisfy the relation: v. of p -v s ＝2v A n/λ p Wherein λ is p Is the wavelength of the pump light, v A Is the acoustic frequency in the fiber and n is the core index. The pump light power needs to be greater than the stimulated brillouin pump power threshold in the optical fiber.
Further, the pulled direction of the signal light polarization state in step (b) is determined by the incident polarization state position of the pump light, the signal light polarization state is always pulled to the polarization state position of the incident pump light, and since the circular birefringence of the optical fiber is much larger than the random linear birefringence in the launch optical fiber, the evolution equation of the signal light polarization state is as follows:
Figure BDA0002884443920000031
wherein
Figure BDA0002884443920000032
For the signal light polarization state Stokes vector, r 0 Is the SBS gain coefficient, I p For pumping light power, the equation shows
Figure BDA0002884443920000033
The equation holds true only in relation to the SBS effect and not in relation to the birefringence of the fiber, as long as the circular birefringence of the fiber is much larger than the random birefringence due to the fiber coiling.
For the conventional SPUN fiber, the beat length of the circular birefringence in the SPUN fiber is 10 -4 Of order much greater than the linear birefringence induced by the coiling of the fiber and the applied stress (10) -6 ～10 -8 ) Magnitude, and therefore the equation holds. The equations theoretically indicate that in a Spun fiber, the signal light polarization will be directed toward the incident pump light polarization regardless of the random birefringence introduced by the fiber internal structural asymmetry or external twist.
Further, the circular birefringent optical fiber Mach-Zehnder interference structure in the step (a) comprises a circular birefringent optical fiber and a splitting ratio K 1 ∶(1-K 1 ) And K 2 ∶(1-K 2 ) The circular birefringent fiber coupler of (1). The light splitting ratio of the coupler, the length of two interference arms of a Mach-Zehnder interference structure and the power of input pump light meet the following relations under the condition of equal-power interference:
Figure BDA0002884443920000034
the directional traction of the pump light to the signal light polarization state is related to the length of a circular birefringent optical fiber interference arm of a Mach-Zehnder interference structure, and the longer the optical fiber is, the longer the action distance of stimulated Brillouin scattering is, and the larger the degree of the polarization traction to the signal light polarization state is.
Technical effects
Compared with the prior art, the invention provides a nonlinear polarization control method based on the nonlinear polarization effect that the polarization state of signal light is directionally pulled to the polarization state of incident pump light in the circular birefringent fiber by stimulated Brillouin scattering, a Mach-Zehnder interference structure is constructed by using the circular birefringent fiber, and the pump light which is transmitted reversely is added to generate the nonlinear stimulated Brillouin scattering effect with the signal light in the interference arms of the two circular birefringent fibers, so that the directional pulling of the polarization state of the pump light to the polarization state of the signal light is realized. The output polarization states of the forward transmitted signal lights in the two interference arms are pulled to the polarization state position of the pump light which is incident reversely, so that the interference polarization noise of the signal lights caused by random stress birefringence is eliminated. Unlike polarization maintaining fibers, their physical mechanism is not consistent. The polarization maintaining fiber is a linear birefringent fiber, and in the polarization maintaining fiber, the polarization state of the signal light is drawn to one of two main axes of the polarization maintaining fiber (specifically determined by the position of the polarization state of the incident pump); in the circular birefringent fiber, the polarization state of the signal light is drawn toward the polarization state of the incident pump light.
The conception, specific structure and technical effects of the present invention will be further described in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention.
Drawings
FIG. 1 is a diagram showing a nonlinear polarization controlled circular birefringent optical fiber Mach-Zehnder interference system of example 1 of this invention;
fig. 2 is a diagram showing a nonlinear polarization controlled circular birefringent optical fiber Mach-Zehnder interference system of example 2 of the present invention.
Detailed Description
The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.
The "circular birefringent optical fiber Mach-Zehnder interference structure" referred to herein is in simplified form as a "Mach-Zehnder interference structure"; the "SBS effect" refers to the stimulated brillouin scattering effect. The directional words "forward" and "reverse" herein refer to: the direction in which the signal light enters the Mach-Zehnder interference structure is referred to as "forward direction", and then a port for receiving the signal light in the Mach-Zehnder interference structure is a "forward direction port"; the direction in which the pump light enters the Mach-Zehnder interference structure is referred to as "reverse", and then the port for receiving the entry of the pump light in the Mach-Zehnder interference structure is the "reverse port".
The term "connected" and the like are to be understood broadly, e.g., as being fixedly connected, detachably connected, or integrated; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or may be interconnected between two elements or may be in an interactive relationship between the two elements. Unless otherwise specifically defined, specific meanings of the above terms in the present invention can be understood as specific conditions by those of ordinary skill in the art.
The principle of the invention is as follows: the method is characterized in that a circular birefringent optical fiber Mach-Zehnder interference structure is constructed based on a polarization directional traction effect of a nonlinear stimulated Brillouin scattering effect in a circular birefringent optical fiber, namely, the polarization state of signal light in the stimulated Brillouin scattering effect is always evolved towards the position of the polarization state of incident pump light under the action of the pump light, and the signal light are subjected to stimulated Brillouin scattering in an optical fiber ring through an additional reverse pump light source, so that the traction of the polarization state of the signal light is realized. The light passes through the circular double-refraction optical fiber coupler, so that the initial polarization states of the pump light entering the two interference arms are ensured to be the same, the polarization states of the output signal light of the two interference arms are pulled to the same polarization state position, and the interference polarization noise of the signal light caused by random stress double refraction in the optical fiber is weakened.
When the frequency v of the pump light p Sum signal light frequency v s Satisfy the relation: v. of p -v s ＝2v A n/λ p (wherein λ) p Is the wavelength of the pump light, v A Is the acoustic frequency in the optical fiber, n is the refractive index of the fiber core), and when the pump light power is greater than the SBS threshold power, in two circular birefringent optical fiber interference arms of the Mach-Zehnder interference system, the nonlinear SBS effect occurs between the signal light transmitted in the forward direction and the pump light transmitted in the reverse direction, and the evolution equation of the polarization state of the signal light can be deduced as follows:
Figure BDA0002884443920000051
wherein
Figure BDA0002884443920000052
For the signal light polarization state Stokes vector, r 0 Is the SBS gain coefficient, I p In order to pump the optical power of the light,
Figure BDA00028844439200000511
the input end is pumped with the optical polarization state Stokes vector.
When pump depletion is not considered, the solution of differential equation (1) is:
Figure BDA0002884443920000053
wherein:
Figure BDA0002884443920000054
Figure BDA0002884443920000055
for the polarization states of the incident signal light and the pump light, I p0 Is reversely input pump light power, M T Is a transposed mueller matrix of fibers from output to input. Signal light gain of
Figure BDA0002884443920000056
L is the length of the optical fiberAnd (4) degree. Adjusting the polarization state of the incident signal light in relation to the polarization state of the incident signal light
Figure BDA0002884443920000057
Then, the maximum SBS gain obtained is:
Figure BDA0002884443920000058
(2) the formula shows that, in the circularly birefringent optical fiber, along the signal light propagation direction, when the optical fiber is sufficiently long,
Figure BDA0002884443920000059
i.e. the signal light of any incident polarization state and the incident polarization state are
Figure BDA00028844439200000510
The SBS effect occurs between the counter-propagating pump lights, and the polarization state of the signal light will be pulled toward the location where the incident polarization state of the pump light is located. In practical systems, the birefringence of random lines introduced by coiling of optical fibers is generally 10 -6 ～10 -8 Much smaller than a circularly birefringent fiber (e.g., round birefringence of a round fiber of the order of 10 -4 Left and right). Therefore, the polarization evolution of the signal light in the propagation process is mainly determined by the circular birefringence of the optical fiber and the SBS polarization pulling, and the polarization state of the signal light is pulled and bound to the polarization state of the input pump light at the output end. In the circular birefringent optical fiber Mach-Zehnder interference structure, as long as the incident polarization states of the reversely transmitted pump light at the output ends of the two interference arms are ensured to be the same, the signal light transmitted in the forward direction in the two interference arms is simultaneously pulled to the incident pump light polarization state. The above formula also shows that the larger the incident pump light power, the larger the traction force; the longer the active fiber, the stronger the pulling effect.
Example 1
As shown in figure 1, the circular birefringent optical fiber Mach-Zehnder interference structure has a light splitting ratio of K 1 ∶(1-K 1 ) A circular birefringent optical fiber coupler 4 having a length L 1 Has a length L of the first circularly birefringent fiber 5 2 Second circular birefringenceOptical fiber 6 and a splitting ratio K 2 ∶(1-K 2 ) And a circular birefringent optical fiber coupler 7. Frequency v s After passing through the first isolator 2, the signal light 1 is subjected to polarization state adjustment through the first polarization controller 3, so that the SBS gain in the interference arm reaches the maximum, enters from the port I of the circular birefringent optical fiber coupler 4, is output from the port III and the port IV, and the output power distribution ratio is K 1 ∶(1-K 1 ) And respectively enter two circular birefringent fiber interference arms. Frequency v p The pump light 11 is amplified in power by the optical amplifier 10, passes through the second isolator 9, is adjusted in polarization state by the second polarization controller 8, and is input from the port of the circular birefringent fiber coupler 8, is output from the ports of the fifth and sixth, and reversely enters the two interference arms of the Mach-Zehnder interference structure. The polarization state of the output pump light of the fifth port and the sixth port is the same, and the optical power is respectively K 2 I p0 And (1-K) 2 )I p0 . In the two interference arms, the forward transmission signal light and the backward transmission pump light generate SBS effect. The signal lights of the two interference arms are converged by the sixth port and the sixth port of the second circular birefringent fiber coupler 8. The net gains of the two interference signals output by the eight ports are respectively
Figure BDA0002884443920000061
And
Figure BDA0002884443920000062
where α is the fiber loss. Selecting two circular birefringent couplers to satisfy the relation:
Figure BDA0002884443920000063
the output optical power of the signal light of the two interference arms can be equal. Due to the SBS effect in the circular birefringent fiber, the polarization state of the signal light is dragged by the SBS polarization of the reversely transmitted pump light, so that the output polarization state of the signal light in the two interference arms is constrained to the polarization state position of the incident pump light, and the polarization interference noise can be eliminated.
Example 2
As shown in fig. 2, the key of the circular birefringent optical fiber Mach-Zehnder interference system based on nonlinear polarization control is to ensure that the initial polarization states of the signal light injected into the Mach-Zehnder interference system in the forward direction are the same in the two interference arms, and the initial polarization states of the pump light injected into the Mach-Zehnder interference system in the reverse direction are the same in the two interference arms, so that any space or waveguide structure can be adopted, and a 2x2 coupling device capable of ensuring that the polarization states in the coupling region are maintained or changed synchronously can be applied to the system.
In the system, the circular birefringent optical fiber Mach-Zehnder interference structure has a light splitting ratio of K 1 ∶(1-K 1 ) A first waveguide splitter 4 of length L 1 Has a length L of the first circularly birefringent fiber 5 2 And a second circularly birefringent optical fiber 6, and a splitting ratio of K 2 ∶(1-K 2 ) And a second waveguide splitter 7. Wherein the length L of the interference arm 1 ，L 2 The optical fiber loss coefficient alpha and the light splitting coefficient of the optical fiber/waveguide splitter satisfy the relation:
Figure BDA0002884443920000064
frequency v s The signal light 1 passes through the first isolator 2, the polarization state is adjusted by the first polarization controller 2, the SBS gain reaches the maximum, and then the signal light enters the circular birefringent optical fiber Mach-Zehnder interference structure from the port I of the first waveguide splitter 4 in the positive direction; frequency v p After the pump light 11 is subjected to power amplification through the optical amplifier 10 and is isolated by the second isolator 9, the polarization state is adjusted through the second polarization controller 8, so that the SBS gain is maximized; and then the optical fiber is branched by a port of the waveguide branching device 7, output by ports of the fifth and sixth, and reversely enter two interference arms of a Mach-Zehnder interference structure. The output pump light polarization states of the fifth port and the sixth port are the same, and the light power is respectively K 2 I p0 And (1-K) 2 )I p0 . In the two interference arms, the forward transmission signal light and the backward transmission pump light generate SBS effect. The signal lights of the two interference arms are converged via the # and # ports of the waveguide splitter 7. SignalThe polarization state of light is dragged by SBS polarization of the reverse transmission pump light, so that the output polarization state of the signal light in the two interference arms is constrained to the polarization state position of the incident pump light, the polarization states of the two paths of interference light are kept consistent, and the polarization interference noise is eliminated. Selecting the length L of the interference arm 1 ，L 2 The optical fiber loss coefficient alpha, the light splitting coefficient of the optical fiber/waveguide splitter and the incident pump light power satisfy the relational expression
Figure BDA0002884443920000065
The optical power of the two interference signals can be kept the same.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims (8)

1. A circular birefringent optical fiber Mach-Zehnder interference system based on nonlinear polarization control is characterized by comprising a first isolator, a first polarization controller, a circular birefringent optical fiber Mach-Zehnder interference structure, a second polarization controller, an optical amplifier and a second isolator,
the output end of the first isolator is connected with one end of the first polarization controller, and the other end of the first polarization controller is connected with one side of the circular birefringent optical fiber Mach-Zehnder interference structure; the input end of the second isolator is connected with the output end of the optical amplifier, the output end of the second isolator is connected with one end of the second polarization controller, and the other end of the second polarization controller is connected with the other side of the circular birefringent optical fiber Mach-Zehnder interference structure;
frequency v p The pump light enters from the reverse port of the circular birefringent optical fiber Mach-Zehnder interference structure after passing through the optical amplifier and the second isolator, and the frequency is v s Signal light ofAfter passing through the first isolator, the optical fiber enters from a positive port of the circular birefringent optical fiber Mach-Zehnder interference structure, a stimulated Brillouin scattering effect occurs between the pump light propagating in the positive direction and the signal light propagating in the reverse direction in two interference arms of the circular birefringent optical fiber Mach-Zehnder interference structure, and the polarization state of the signal light propagating in the positive direction in the two interference arms is pulled to the position of the polarization state of the incident pump light;
the circular birefringent optical fiber Mach-Zehnder interference structure comprises a first circular birefringent optical fiber coupler, a first circular birefringent optical fiber, a second circular birefringent optical fiber and a second circular birefringent optical fiber coupler, wherein one port on one side of the first circular birefringent optical fiber coupler is connected with the first polarization controller, and two ends on the other side of the first circular birefringent optical fiber coupler are respectively connected with the first circular birefringent optical fiber and the second circular birefringent optical fiber; the other ports of the first circular birefringent fiber and the second circular birefringent fiber are connected with the two ports on the same side of the second circular refractive fiber coupler; and one port on the other side of the second circular birefringent fiber coupler is connected with the second polarization controller.
2. The non-linear polarization control-based circularly birefringent fiber Mach-Zehnder interference system of claim 1, wherein the first circularly birefringent fiber coupler splitting ratio is K 1 :(1-K 1 ) (wherein 0. ltoreq. K 1 ≦ 1) 2 × 2 coupling device with the polarization state of the coupling region maintained constant or varied synchronously, including a circularly birefringent fiber coupler.
3. The non-linear polarization control-based circularly birefringent fiber Mach-Zehnder interference system of claim 1, wherein the second circularly birefringent fiber coupler split ratio is K 2 :(1-K 2 ) (wherein 0. ltoreq. K 2 ≦ 1) 2 × 2 coupling device with the polarization state of the coupling region maintained constant or varied synchronously, including a circularly birefringent fiber coupler.
4. The non-linear polarization control-based circularly birefringent fiber Mach-Zehnder interference system of claim 1, wherein the first circle isThe length of the birefringent fiber is L 1 The second circular birefringent fiber has a length L 2 Wherein (L) 1 、L 2 ＞0)。
5. A nonlinear polarization control method of a circular birefringent optical fiber Mach-Zehnder interferometer system based on nonlinear polarization control as defined in any of claims 1-4, comprising the steps of:
(a) frequency is nu s Signal light and frequency of v p The pump light is simultaneously input into the circular birefringent optical fiber Mach-Zehnder interference structure through a forward port and a reverse port of the circular birefringent optical fiber Mach-Zehnder interference system based on the nonlinear polarization control;
(b) the input pump light and the signal light are respectively transmitted in opposite directions in the two interference arms, a stimulated Brillouin scattering effect is generated between the signal light transmitted in the forward direction and the pump light transmitted in the reverse direction, and the polarization state of the signal light transmitted in the forward direction is pulled by the polarization of the pump light transmitted in the reverse direction, so that the output polarization state of the output signal light in the two interference arms of the Mach-Zehnder interference structure is simultaneously pulled to the same incident pump light polarization state position.
6. The nonlinear polarization control method of claim 5, wherein the frequency v of the pump light in the step (a) is p And a frequency v of the signal light s Satisfy the relation: v is p -ν s ＝2ν A n/λ p Wherein λ is p Is the wavelength of the pump light, v A Is the acoustic frequency in the fiber and n is the core index.
7. The nonlinear polarization control method of claim 5, wherein the pulled direction of the polarization state of the signal light in step (b) is determined by the incident polarization state position of the pump light, the polarization state of the signal light is always pulled to the polarization state position of the incident pump light, and in the Spun fiber, since the circular birefringence of the fiber is much larger than the random linear birefringence, the evolution equation of the polarization state of the signal light is:
Figure FDA0003661238580000021
wherein
Figure FDA0003661238580000022
Normalized polarization Stokes vectors, r, of the signal light and the pump light, respectively 0 Is the SBS gain coefficient, I p For the pump light power, the equation shows
Figure FDA0003661238580000023
The equation holds true only in relation to the SBS effect and not in relation to the birefringence of the fiber, as long as the circular birefringence of the fiber is much larger than the random birefringence due to fiber coiling and perturbation.
8. The nonlinear polarization control method of claim 5, wherein the circular birefringent fiber Mach-Zehnder interference structure in the step (a) includes two circular birefringent fiber interference arm lengths L1, L2, and a spectral coefficient K of the first and second optical circular birefringent fiber couplers 1 、K 2 Optical fiber loss coefficient alpha, SBS gain coefficient r 0 Input pump light power I p0 Obeying the following relation according to the equal interference light intensity condition:
Figure FDA0003661238580000024
CN202110009326.0A 2021-01-05 2021-01-05 Nonlinear polarization control system and method for circular birefringent optical fiber Mach-Zehnder interference system Active CN112835244B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110009326.0A CN112835244B (en) 2021-01-05 2021-01-05 Nonlinear polarization control system and method for circular birefringent optical fiber Mach-Zehnder interference system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110009326.0A CN112835244B (en) 2021-01-05 2021-01-05 Nonlinear polarization control system and method for circular birefringent optical fiber Mach-Zehnder interference system

Publications (2)

Publication Number Publication Date
CN112835244A CN112835244A (en) 2021-05-25
CN112835244B true CN112835244B (en) 2022-09-16

Family

ID=75925940

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110009326.0A Active CN112835244B (en) 2021-01-05 2021-01-05 Nonlinear polarization control system and method for circular birefringent optical fiber Mach-Zehnder interference system

Country Status (1)

Country Link
CN (1) CN112835244B (en)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030215173A1 (en) * 2002-05-14 2003-11-20 Farhad Hakimi Multiphase optical pulse generator
CN101742738B (en) * 2009-10-13 2012-11-07 北京邮电大学 Full duplex optical carrier radio frequency RoF link system
CN101706280A (en) * 2009-11-27 2010-05-12 北京航空航天大学 Optical path structure for stimulated Brillouin optical fiber gyroscope
CN107238991B (en) * 2017-05-17 2019-10-11 上海大学 A kind of modulating system and method based on stimulated Brillouin scattering gain spectra

Also Published As

Publication number Publication date
CN112835244A (en) 2021-05-25

Similar Documents

Publication Publication Date Title
Kaminow Polarization in optical fibers
CA1268365A (en) Fiber optic bidirectional data bus tap
CN106225666B (en) Quantum optical fiber interferometer
EP3973337A1 (en) Integrated optical polarizer and method of making same
JPH0895095A (en) Dispersion compensator and light amplifier
JP2594771B2 (en) Low loss dual mode optical fiber compensator
Liu et al. Erbium-doped fiber ring laser based on few-mode-singlemode-few-mode fiber structure for refractive index measurement
CN106338797B (en) A kind of optoisolator light path system
CA2309564C (en) Method of manufacturing polarization-maintaining optical fiber coupler
Okamoto et al. High-birefringence polarizing fiber with flat cladding
CN102279444A (en) Passive device for eliminating polarization noise in Brillouin optical fiber sensor
Lin et al. Wide-angle low-loss single-mode symmetric Y-junctions
CN112835244B (en) Nonlinear polarization control system and method for circular birefringent optical fiber Mach-Zehnder interference system
CN112612076B (en) Few-mode multi-core microstructure optical fiber and few-mode optical fiber amplifier
Takada et al. Ultimate limit of polarization cross talk in birefringent polarization-maintaining fibers
US6959131B2 (en) Achromatic fiber-optic power splitter and related methods
US5195149A (en) Fiber optic amplifier
CN111366146B (en) Nonlinear polarization control method of polarization-maintaining optical fiber Sagnac interference system
Liang Relation between transition loss and mode-field half-width for curved noncircular weakly-guiding single-mode waveguides
JPH0854525A (en) Fiber type dispersion compensating device
Zhang et al. Design of taper coupler type polarization splitter with single-polarization photonic crystal fiber
Morishita et al. Fiber loop polarizers using a fused taper coupler
Saktioto et al. Simplified Linear Configuration Model of 3x3 Single Mode Fiber Coupler using Matrix Transfer
Su et al. Stress birefringence in the three-core optical fiber and its effects on the transmission property
Zhang Study on Optical Devices Based on Single-Polarization Photonic Crystal Fiber

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant