CN201408305Y - Differential phase shift keying signal demodulator - Google Patents

Abstract

The utility model provides a differential phase shift keying signal demodulator, which comprises a Mach-Zendaal interferometer. The interferometer is provided with an input port, two output ports, a first arm and a second arm, wherein the first arm is located between the input port and one output port, and the second arm is located between the input port and the other output port. The input port is equipped with an incident fiber collimator, each output port is equipped with an emergent fiber collimator, a photoelectric conversion unit is connected with the two emergent fiber collimators, wherein the Mach-Zendaal interferometer is an equi-arm interferometer, and one of the first arm and the second arm is equipped with a first delay block. The differential phase shift keying signal demodulator can effectively avoid change of optical path difference of the two arms of the interferometer caused by temperature change, and reduces sensitivity of the interferometer to the temperature change,thereby increasing working stability of the differential phase shift keying signal demodulator.

Description

The differential phase keying (DPSK) demodulator of PM signal PM

Technical field

The utility model relates to a kind of differential phase keying (DPSK) demodulator of PM signal PM, specifically, is based on Mach-the increase differential phase keying (DPSK) demodulator of PM signal PM that the Da Er interferometer is realized.

Background technology

Along with Internet development, people propose more and more higher requirement to the capacity of Fiber Optical Communication System and the transfer rate of Fiber Optical Communication System.Existing Fiber Optical Communication System adopts close wavelength-division multiplex technology, transmits wavelength optical signals on same optical fiber, to reach the purpose that improves traffic capacity.But because the continuous increase of bandwidth applications as application such as video conference, interconnection type Web TVs, makes the capacity of Fiber Optical Communication System be subjected to unprecedented pressure.

For addressing the above problem, some Fiber Optical Communication System adopt the differential phase keying (DPSK) technology, can transmit the data-signal of per second 40Gb on optical fiber communication network, and capacity pressure is alleviated.Because existing Fiber Optical Communication System is used the light intensity signal of light intensity receiver receiving intensity size variation, therefore, when using the differential phase keying (DPSK) technology, need to use a differential phase keying (DPSK) demodulator of PM signal PM, convert the phase change of light signal to Strength Changes, so that the light intensity receiver receives.

The structure principle chart of existing a kind of differential phase keying (DPSK) demodulator of PM signal PM as shown in Figure 1, the differential phase keying (DPSK) demodulator of PM signal PM has the Mach of a unequal arm-increase Da Er interferometer 10, interferometer 10 has an input port 11 and two output ports 12,13,11 places are provided with input optical fibre collimating apparatus 31 at input port, and output port 12,13 places are provided with output optical fibre collimating apparatus 32,33 respectively.Output optical fibre collimating apparatus 32,33 is connected with photoelectric switching circuit 35, and the light signal that receives is sent to photoelectric switching circuit 35.

Mach-increase Da Er interferometer 10 and have two beam splitters, therein on beam splitter, be provided with semi-transparent semi-reflecting lens 15 and total reflective mirror 17 abreast, on another beam splitter, be provided with total reflective mirror 18 and semi-transparent semi-reflecting lens 16 abreast, and semi-transparent semi-reflecting lens 15,16, total reflective mirror 17,18 all show with the angle of inclination to be that 45 ° of modes are arranged by Fig. 1, and the distance between semi-transparent semi-reflecting lens 15 and the total reflective mirror 17 is d, and the distance between semi-transparent semi-reflecting lens 16 and the total reflective mirror 18 also is d.

When the light beam b10 of input optical fibre collimating apparatus 31 along continuous straight runs outgoing is mapped to semi-transparent semi-reflecting lens 15, be divided into transmitted light beam b11 and folded light beam b12, transmitted light beam b11 along continuous straight runs is incident to semi-transparent semi-reflecting lens 16, folded light beam b12 then is incident to total reflective mirror 17, form folded light beam b13 afterwards, folded light beam b13 forms folded light beam b14 through total reflective mirror 18 and is incident in the semi-transparent semi-reflecting lens 16.

Transmitted light beam b11 forms orthogonal transmitted light beam and folded light beam through semi-transparent semi-reflecting lens 16, and folded light beam b14 also forms orthogonal transmitted light beam and folded light beam through behind the semi-transparent semi-reflecting lens 16.Because transmitted light beam b11 is identical through the folded light beam direction that semi-transparent semi-reflecting lens 16 forms with folded light beam b14 through the direction of the transmitted light beam that semi-transparent semi-reflecting lens 16 forms, and interfere at semi-transparent semi-reflecting lens 16 places, form light beam b15 and outgoing to output optical fibre collimating apparatus 32; Simultaneously, transmitted light beam b11 is also identical through the transmitted light beam direction that semi-transparent semi-reflecting lens 16 forms with folded light beam b14 through the direction of the folded light beam that semi-transparent semi-reflecting lens 16 forms, and interfere at semi-transparent semi-reflecting lens 16 places, form light beam b16 outgoing to output optical fibre collimating apparatus 33.

Therefore, light beam b10 is divided into the two-way light path by semi-transparent semi-reflecting lens 15 and arrives semi-transparent semi-reflecting lens 16, and wherein one road light path is the light path of transmitted light beam b11 process, forms the first arm of interferometer 10, another road light path is the light path of folded light beam b12, b13, b14 process, forms second arm of interferometer 10.As shown in Figure 1, the optical path difference OPD of the first arm of interferometer 10 and second arm is

OPD=2d (formula 1)

In the formula 1, d is the distance between two light beams.

Therefore, can be by selecting appropriate beam splitter material, and set between semi-transparent semi-reflecting lens 15 and the total reflective mirror 17 apart from d, can determine the optical path difference OPD of interferometer 10 the first arms and second arm.In the differential phase keying (DPSK) technology, the mistiming that the light signal that the first arm and second arm transmit needs should be transmits the required time of 1 Bit data, therefore, can realize this mistiming by the optical path difference OPD that sets between the first arm and second arm.

Because when transmitted light beam b11 and folded light beam b14 process semi-transparent semi-reflecting lens 16, light beam b15 and b16 that the two light beams that forms on same direction interferes back formation have light intensity to change, thereby realize that light signal converts Strength Changes to from phase change.Photoelectric switching circuit 35 promptly is convertible into corresponding electric signal after receiving light signal by output optical fibre collimating apparatus 32,33, realizes the demodulation to signal among the light beam b10.

But, along with variation of temperature, the beam splitter of making by materials such as fused quartz or optical glass refractive index can vary with temperature, thereby change the optical path difference OPD between interferometer 10 the first arms and second arm, the light signal time-delay that causes the first arm and second arm to transmit is greater than or less than and transmits the required time of 1 Bit data, so that the signal generation error after photoelectric switching circuit 35 demodulation, the job stability of reduction differential phase keying (DPSK) demodulator of PM signal PM.

Summary of the invention

Fundamental purpose of the present utility model provides a kind of to the insensitive differential phase keying (DPSK) demodulator of PM signal PM of temperature variation;

Another purpose of the present utility model provides the higher differential phase keying (DPSK) demodulator of PM signal PM of a kind of job stability.

For realizing above-mentioned fundamental purpose, the differential phase keying (DPSK) demodulator of PM signal PM that the utility model provides comprises Mach-increase the Da Er interferometer, interferometer has an input port and two output ports, the first arm and second arm between input port and another output port between input port and output port, and input port is provided with the incident optical collimating apparatus, each output port is provided with an outgoing optical fiber collimator, one photoelectric conversion unit is connected with two outgoing optical fiber collimators, wherein, Mach-increase the Da Er interferometer and be equiarm Mach-increase Da Er interferometer, an arm in the first arm and second arm are provided with first piece of delaying time.

By such scheme as seen, the differential phase keying (DPSK) demodulator of PM signal PM has equiarm Mach-increase Da Er interferometer, and the first time-delay piece is set on one of them arm of two arms, and light beam produces time-delay when delaying time piece through first, thereby realizes the mistiming that light beam transmits between two arms.The problem that the two arm optical path differences that the time-delay of using the time-delay piece to realize that light beam transmits can effectively avoid beam splitter to cause because of temperature variation change makes the differential phase keying (DPSK) demodulator of PM signal PM insensitive to temperature variation, improves job stability.

A preferred scheme is, the first time-delay piece is by to the insensitive material of steady change, make as quartz etc., and the first time-delay piece is the constant time lag piece.Like this, during temperature change, the length variations of the first time-delay piece is very little, can ignore, and guarantees that thus the first arm of interferometer and the mistiming that second arm transmits light signal are fixed as the transmission required time of 1 Bit data.

Description of drawings

Fig. 1 is the structure principle chart of existing differential phase keying (DPSK) demodulator of PM signal PM;

Fig. 2 is equiarm Mach-the increase structure principle chart of Da Er interferometer;

Fig. 3 is the structure principle chart of the utility model first embodiment;

Fig. 4 is the structure principle chart of the utility model second embodiment.

The utility model is described in further detail below in conjunction with drawings and Examples.

Embodiment

The utility model is used equiarm Mach-increase Da Er interferometer and is realized control to light signal, simply introduces equiarm Mach-the increase principle of work that Da Er interferes below in conjunction with Fig. 2.

Equiarm Mach-increase Da Er interferometer 40 has an input port 41 and two output ports 42,43, and have a pair of beam splitting that is equal to-total internal reflection mirror 61,62, and between beam splitting-total internal reflection mirror 61,62, be provided with a rectangular parallelepiped prism 63 that is manufactured from the same material.And beam splitting-total internal reflection mirror 61,62 and rectangular parallelepiped prism 63 are integral through optical contant, form a stable monomer Mach-increase Da Er interferometer.

Beam splitting-total internal reflection mirror 61 has semi-transparent semi-reflecting lens 45 and total reflective mirror 46, and beam splitting-total internal reflection mirror 62 has semi-transparent semi-reflecting lens 47 and total reflective mirror 48, and the angle of inclination of semi-transparent semi-reflecting lens 45,47 and total reflective mirror 46,48 is 45 °.Among Fig. 2, two semi-transparent semi-reflecting lens 45,47 of equiarm Mach-increase Da Er interferometer 40 are the semi-transparent semi-reflecting lens with polarization irrelevant, promptly equate with reflected beam energy through semi-transparent semi-reflecting lens 45,47 formed transmitted light beams.

Incident beam b20 is divided into two light beams after inciding semi-transparent semi-reflecting lens 45, is respectively transmitted light beam b21 and folded light beam b22, and transmitted light beam b21 incides total reflective mirror 48 back formation folded light beam b24 and incides in the semi-transparent semi-reflecting lens 47.Folded light beam b22 is incident to total reflective mirror 46 back formation folded light beam b23 and is incident in the semi-transparent semi-reflecting lens 47.

The transmitted light beam that folded light beam b23 passes through semi-transparent semi-reflecting lens 47 through the folded light beam of semi-transparent semi-reflecting lens 47 and folded light beam b24 is interfered on semi-transparent semi-reflecting lens 47 and is formed light beam b25, the transmitted light beam of folded light beam b23 process semi-transparent semi-reflecting lens 47 and folded light beam is crossed semi-transparent semi-reflecting lens 47 through b24 folded light beam are interfered on semi-transparent semi-reflecting lens 47 and are formed light beam b26, and two light beams b25, b26 export through the output port 42,43 of interferometer 40 respectively.

At equiarm Mach-increase in the Da Er interferometer 40, the two-way light path respectively by the light path of light beam b21,24 processes of b and light beam b22, b23 the light path of process form, also just form the first arm and second arm of interferometer 40.Because the two-way equivalent optical path, the optical path difference OPD of so equiarm Mach-increase 40 liang of arms of Da Er interferometer is zero.

Referring to Fig. 3, has an equiarm Mach-increase Da Er interferometer 40 according to the differential phase keying (DPSK) demodulator of PM signal PM of the utility model first embodiment, 41 places are provided with input optical fibre collimating apparatus 31 at interferometer 40 input ports, output port 42,43 places are provided with output optical fibre collimating apparatus 32,33 respectively, and output optical fibre collimating apparatus 32,32 is connected with photoelectric switching circuit 35.

In the present embodiment, be provided with the first time-delay piece 51 between semi-transparent semi-reflecting lens 45 and the total reflective mirror 48, just being provided with the first time-delay piece, 51, the first time-delay pieces 51 on the first arm of interferometer 40 is the constant time lag piece, and promptly its length L 1 on optical path direction is non-adjustable.Simultaneously, the first time-delay piece 51 is made as materials such as quartz by to the insensitive material of temperature variation.Transmitted light beam b31 produces time-delay when delaying time piece 51 through first, being light beam b31 time of inciding total reflective mirror 48 from semi-transparent semi-reflecting lens 45 is incident to time of semi-transparent semi-reflecting lens 47 greater than folded light beam b33 from total reflective mirror 46, and the mistiming that two light beams transmits is the time that 1 Bit data transmits.

For transfer rate is the Fiber Optical Communication System of per second 40Gb, and optical path difference is 7.5 millimeters between interferometer 40 the first arms and second arm, and therefore, the length L 1 of the first time-delay piece 51 is

$L1=\frac{7.5}{n1-1}$ (formula 2)

In the formula 2, n1 is the refractive index of the first time-delay piece, 51 manufactured materials.Therefore, select the manufactured materials and the length L 1 of the first suitable time-delay piece 51, can realize that 40 liang of arms of interferometer transmit the optical path difference of light beam, realize the conversion of the phase shift variations of light signal to Strength Changes.The light signal that photoelectric switching circuit 35 receives 32,33 outputs of output optical fibre collimating apparatus converts thereof into corresponding electric signal, can realize the demodulation of signal.

The differential phase keying (DPSK) demodulator of PM signal PM of present embodiment adopts the Mach of equiarm-increase Da Er interferometer 40, avoid beam splitter to answer temperature variation and the mode length variations, cause the optical path difference of two arms to change, adopt 51 pairs of the first time-delay pieces wherein the light beam of an arm carry out delay process, can effectively improve the job stability of differential phase keying (DPSK) demodulator of PM signal PM.

Certainly, the length L 1 of ignoring the first time-delay piece 51 among first embodiment varies with temperature the change of generation, varies with temperature the change of generation if consider the length L 1 of the first time-delay piece 51, and then the relation of two arm optical path difference OPD and temperature T is as follows:

$\frac{d\left[\mathrm{OPD}\right]}{\mathrm{dT}}=(n1-1)\×\frac{\mathrm{dL}1}{\mathrm{dT}}+L1\×\frac{\mathrm{dn}1}{\mathrm{dT}}=[(n1-1)\×\mathrm{\α}1+\frac{\mathrm{dn}1}{\mathrm{dT}}]\×L1$ (formula 3)

In the formula 3, α 1 is the linear expansion coefficients of first time-delay piece 51 manufactured materials during to temperature variation.

Therefore, for fear of the influence that temperature variation causes 40 liang of arm optical path differences of interferometer, can on another arm, increase by the second time-delay piece.

Referring to Fig. 4, be the structure principle chart of second embodiment.Different with first embodiment is that present embodiment increases by the second time-delay piece 52 between total reflective mirror 46 and semi-transparent semi-reflecting lens 47, just increase by the second time-delay piece 52 on second arm of interferometer 40.And the second time-delay piece also is the constant time lag piece, and its length on optical path direction is L2.Preferably, the manufactured materials of the second time-delay piece 52 is different from the manufactured materials of the first time-delay piece 51, and as being made by materials such as silicon, silicon gums, its refractive index is n2, linear expansion coefficient is α 2, and these refractive index n 1 and linear expansion coefficients that all are different from the first time-delay piece, 51 manufactured materials are α 1.

After adding the second time-delay piece 52, the length L 1 of the first time-delay piece 51 is correspondingly changed into

$L1=\frac{7.5}{n1-1}+\frac{(n2-1)\×L2}{n1-1}=\frac{7.5+(n2-1)\×L2}{n1-1}$ (formula 4)

Thus, length L 1, the L2 of the first time-delay piece 51 and the second time-delay piece 52 are respectively with variation of temperature value Δ 1, Δ 2

$\mathrm{\Δ}1=[(n1-1)\×\mathrm{\α}1+\frac{\mathrm{dn}1}{\mathrm{dT}}]\×L1$ (formula 5)

$\mathrm{\Δ}2=[(n2-1)\×\mathrm{\α}2+\frac{\mathrm{dn}2}{\mathrm{dT}}]\×L2$ (formula 6)

As long as select suitable manufactured materials, promptly select the first suitable time-delay piece 51 and refractive index n 1, n2 and linear expansion coefficient α 1, the α 2 of the second time-delay piece 52, can calculate the first suitable time-delay piece 51 and length L 1, the L2 of the second time-delay piece 52, make Δ 1=Δ 2, just the first time-delay piece 51 and second delay time piece 52 when varying with temperature length variations identical.Like this, the optical path difference of interferometer 40 the first arms and second arm is fixed, and transmitted light beam b41 is time that 1 Bit data transmit with folded light beam b43 through second mistiming of delaying time piece 52 through the first time-delay piece 51.

This shows, present embodiment increases by the second time-delay piece 52 on second arm of interferometer 40, be used to compensate the linear expansion that the first time-delay piece 51 varies with temperature generation, reduce the susceptibility of 40 pairs of temperature variation of interferometer, differential phase keying (DPSK) demodulator of PM signal PM job stability is improved greatly.

Because the second time-delay piece 52 is used to compensate the length variations that the first time-delay piece 51 causes with temperature, therefore the length L 2 of the second time-delay piece 52 should be less than the length L 1 of the first time-delay piece 51.Preferably, the xsect of the first time-delay piece 51 and the second time-delay piece 52 is a rectangle, and the variation of angle takes place when avoiding transmitted light beam b41 and folded light beam b43 through the first time-delay piece 51 and the second time-delay piece 52.

Certainly, above-mentioned two embodiment only are preferable embodiments of the present utility model, in the practical application, more change can also be arranged, for example, the first time-delay piece 51 is arranged between total reflective mirror 48 and the semi-transparent semi-reflecting lens 47, the second time-delay piece 52 is arranged between semi-transparent semi-reflecting lens 45 and the total reflective mirror 46; Perhaps the xsect of the first time-delay piece 51, the second time-delay piece 52 is set to the shape that trapezoidal, parallelogram etc. has the pair of parallel limit, and these change does not influence enforcement of the present utility model.

It is emphasized that at last; the utility model is not limited to above-mentioned embodiment, as makes the delay time small variations such as change of block length of the first time-delay piece and change, the first time-delay piece and second of the second time-delay block of material and also should be included in the protection domain of the utility model claim.

Claims (6)

1, the differential phase keying (DPSK) demodulator of PM signal PM comprises

Mach-increase the Da Er interferometer, described interferometer has an input port and two output ports, the first arm and second arm between described input port and another output port between described input port and output port;

Described input port place is provided with the incident optical collimating apparatus, and each output port place is provided with an outgoing optical fiber collimator, and two outgoing optical fiber collimators of a photoelectric conversion unit and this are connected;

It is characterized in that:

Described Mach-increase the Da Er interferometer is equiarm Mach-increase Da Er interferometer, and an arm in described the first arm and second arm is provided with first piece of delaying time.

2, differential phase keying (DPSK) demodulator of PM signal PM according to claim 1 is characterized in that:

The described first time-delay piece is the constant time lag piece, and is made by the temperature-insensitive material.

3, differential phase keying (DPSK) demodulator of PM signal PM according to claim 1 and 2 is characterized in that:

Another arm in the described the first arm and second arm is provided with the second time-delay piece.

4, differential phase keying (DPSK) demodulator of PM signal PM according to claim 3 is characterized in that:

The length of the described second time-delay piece is less than the length of the described first time-delay piece.

5, differential phase keying (DPSK) demodulator of PM signal PM according to claim 3 is characterized in that:

The described second time-delay piece is the constant time lag piece.

6, differential phase keying (DPSK) demodulator of PM signal PM according to claim 3 is characterized in that:

The described second time-delay block of material linear expansion coefficient is different with the described first time-delay block of material linear expansion coefficient.

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