GB2318646A - Optical polarisation scrambling - Google Patents

Optical polarisation scrambling Download PDF

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Publication number
GB2318646A
GB2318646A GB9622245A GB9622245A GB2318646A GB 2318646 A GB2318646 A GB 2318646A GB 9622245 A GB9622245 A GB 9622245A GB 9622245 A GB9622245 A GB 9622245A GB 2318646 A GB2318646 A GB 2318646A
Authority
GB
United Kingdom
Prior art keywords
polarisation
modulator
optical phase
phase modulator
polarisation scrambler
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.)
Withdrawn
Application number
GB9622245A
Other versions
GB9622245D0 (en
Inventor
Ian Haxell
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.)
Alcatel Submarine Networks UK Ltd
Original Assignee
STC Submarine Systems Ltd
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 STC Submarine Systems Ltd filed Critical STC Submarine Systems Ltd
Priority to GB9622245A priority Critical patent/GB2318646A/en
Publication of GB9622245D0 publication Critical patent/GB9622245D0/en
Priority to PCT/GB1997/002939 priority patent/WO1998019406A1/en
Publication of GB2318646A publication Critical patent/GB2318646A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H04B10/532—Polarisation modulation
    • 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
    • G02F1/01—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 for the control of the intensity, phase, polarisation or colour 
    • G02F1/011—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 for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass
    • 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
    • G02F1/01—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 for the control of the intensity, phase, polarisation or colour 
    • G02F1/0136—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 for the control of the intensity, phase, polarisation or colour  for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation
    • G02F1/0139—Polarisation scrambling devices; Depolarisers

Landscapes

  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Optical Integrated Circuits (AREA)

Abstract

A polarisation scrambler is provided which includes an optical phase modulator and an amplitude modulator waveguide. The optical phase modulator requires no misalignment in polarisation state to that which emerges from the amplitude modulator waveguide. In particular, the optical phase modulator and amplitude modulator waveguide are integrated on a single substrate.

Description

IMPROVEMENTS IN OPTICAL POLARISATION SCRAMBLING The present invention relates to Optical Polarisation Scrambling and more particularly but not exclusively to an integrated polarisation scrambling device.
The effects of polarisation dependent hole-burning and polarisation dependent loss are reduced by modulating the state of polarisation (SOP) of an arbitrarily polarised optical signal being launched into the transmission path periodically through a predetermined sequence of polarisation states. The sequence of polarisation states is selected such that on average the launched modulated signal excites substantially all possible polarisation states with substantially equal probability. This function will be known as a polarisation scrambler.
One arrangement which is known to us is to add a polarisation scrambler after the optical amplitude modulator to depolarise the signal light. Because polarisation scramblers require 45 degree optical alignment to the waveguide this necessarily means that the polarisation scrambler cannot be an integrated optical device with the amplitude modulator.
The present invention seeks to improve on the performance available from the previously mentioned arrangement.
According to the invention there is provided a polarisation scrambler comprising an optical phase modulator which requires no misalignment in polarisation state to that which emerges from an amplitude modulator waveguide.
Preferably the two devices are integrated on a single substrate.
In order that the invention and its various other preferred features may be understood more easily, an embodiment thereof will now be described, by way of example only, with reference to the drawing, the single Figure of which is a schematic illustration illustrating the basic features.
Referring to the drawing, depolarisation is achieved by launching phase modulated light into a birefringent element. The launch angle to the elements slow axis must be tightly controlled to be 45 degrees. If the phase modulation depth and birefringence are of sufficient magnitude then complete depolarisation will occur.
The phase modulator creates a series of spectral lines with power spectral density given by the following expression.
where ss represents the phase modulation depth.
Jn = nth order Bessel function If the birefringent element is adjusted to one half of the phase modulation period (with a launch angle bisecting the fast and slow axes) then alternate spectral lines will emerge with orthogonal states of polarisation.
To reduce the degree of polarisation to zero then all that is required is for the power in each of the orthogonal states to be equal. This will occur when the following expression is met for sinusoidal phase modulation.
This can be shown to occur when the phase modulation depth, P-0.38375*7r radians.
The integrated design has an advantage of cost, reliability, space and insertion loss over a discrete amplitude modulator and polarisation scrambler. The device may also offer advantages in line-width broadening over the discrete design for complete depolarisation.

Claims (8)

CLAIMS:
1. A polarisation scrambler comprising an optical phase modulator and an amplitude modulator waveguide in which the optical phase modulator requires no misalignment in polarisation state to that which emerges from the amplitude modulator waveguide.
2. A polarisation scrambler according to claim 1, further comprising a birefringent element arranged to receive light from the optical phase modulator having a launch angle which substantially bisects the fast and slow axis of the birefringent element.
3. A polarisation scrambler according to claim 2, in which the birefringent element is adjusted to one half of the phase modulation period of the optical phase modulator.
4. A polarisation scrambler according to claim 2 or 3, in which the phase modulation depth ss of the optical phase modulator is substantially 0.38375 x pi radians.
5. A polarisation scrambler according to any preceding claim, in which the optical phase modulator and amplitude modulator waveguide are integrated on a single substrate.
6. A polarisation scrambler according to claim 5, in which the substrate is LiNbO3 or GaAs.
7. A polarisation scrambler according to any preceding claim, in which the amplitude modulator is a Mach Zehnder modulator.
8. A polarisation scrambler substantially as shown in and/or described with reference to Figure 1 of the accompanying drawings
GB9622245A 1996-10-25 1996-10-25 Optical polarisation scrambling Withdrawn GB2318646A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB9622245A GB2318646A (en) 1996-10-25 1996-10-25 Optical polarisation scrambling
PCT/GB1997/002939 WO1998019406A1 (en) 1996-10-25 1997-10-24 Improvements in optical polarisation scrambling

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9622245A GB2318646A (en) 1996-10-25 1996-10-25 Optical polarisation scrambling

Publications (2)

Publication Number Publication Date
GB9622245D0 GB9622245D0 (en) 1996-12-18
GB2318646A true GB2318646A (en) 1998-04-29

Family

ID=10801949

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9622245A Withdrawn GB2318646A (en) 1996-10-25 1996-10-25 Optical polarisation scrambling

Country Status (2)

Country Link
GB (1) GB2318646A (en)
WO (1) WO1998019406A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1003299A1 (en) * 1998-11-19 2000-05-24 Alcatel Suppression of brillouin scattering by amplitude modulation and polarisation scrambling
EP1005183A1 (en) * 1998-11-26 2000-05-31 Alcatel Raman effect supression by polarisation modulation

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6819810B1 (en) * 2002-04-09 2004-11-16 Oplink Communications, Inc. Depolarizer

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4384760A (en) * 1980-12-15 1983-05-24 Bell Telephone Laboratories, Incorporated Polarization transformer
US5611005A (en) * 1996-04-26 1997-03-11 Lucent Technologies, Inc. High-speed polarization scrambler with adjustable chirp

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2717331B1 (en) * 1994-02-18 1996-04-05 Cit Alcatel Optical communication system with polarization jammer.
IT1279248B1 (en) * 1995-12-21 1997-12-09 Pirelli Cavi S P A Ora Pirelli MODULATED AND DEPOLARIZED OPTICAL SIGNALS TRANSMISSION SYSTEM
FR2749114B1 (en) * 1996-05-23 1998-06-19 Alcatel Submarcom OPTICAL COMMUNICATION SYSTEM WITH OPTICAL AMPLIFIERS WHOSE GAIN DEPENDS ON POLARIZATION OF THE INPUT SIGNAL

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4384760A (en) * 1980-12-15 1983-05-24 Bell Telephone Laboratories, Incorporated Polarization transformer
US5611005A (en) * 1996-04-26 1997-03-11 Lucent Technologies, Inc. High-speed polarization scrambler with adjustable chirp

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IEEE Journal on selected topics in Quantum Electronics vol.2no. 2 pages 311-8 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1003299A1 (en) * 1998-11-19 2000-05-24 Alcatel Suppression of brillouin scattering by amplitude modulation and polarisation scrambling
WO2000031903A1 (en) * 1998-11-19 2000-06-02 Alcatel Suppression of brillouin effect by amplitude modulation and polarization scrambling
FR2789827A1 (en) * 1998-11-19 2000-08-18 Cit Alcatel SUPPRESSION OF THE BRILLOUIN EFFECT BY AMPLITUDE MODULATION AND POLARIZATION INTERFERENCE
EP1005183A1 (en) * 1998-11-26 2000-05-31 Alcatel Raman effect supression by polarisation modulation
FR2786638A1 (en) * 1998-11-26 2000-06-02 Cit Alcatel SUPPRESSION OF THE RAMAN EFFECT BY MODULATING POLARIZATION
US6344923B1 (en) 1998-11-26 2002-02-05 Alcatel Eliminating the Raman effect by modulating polarization

Also Published As

Publication number Publication date
WO1998019406A1 (en) 1998-05-07
GB9622245D0 (en) 1996-12-18

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