GB2267405A - Polarization control in an optical transmission system - Google Patents
Polarization control in an optical transmission system Download PDFInfo
- Publication number
- GB2267405A GB2267405A GB9310665A GB9310665A GB2267405A GB 2267405 A GB2267405 A GB 2267405A GB 9310665 A GB9310665 A GB 9310665A GB 9310665 A GB9310665 A GB 9310665A GB 2267405 A GB2267405 A GB 2267405A
- Authority
- GB
- United Kingdom
- Prior art keywords
- polarization
- signal light
- state
- terminal equipment
- error rate
- 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.)
- Granted
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
- H04B10/25—Arrangements specific to fibre transmission
-
- 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
- H04B10/29—Repeaters
- H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
- H04B10/293—Signal power control
- H04B10/2933—Signal power control considering the whole optical path
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Optical Communication System (AREA)
Abstract
Polarization control is used in an optical communication system that includes as repeaters optical amplifiers whose output signal power fluctuates according to the state of polarization of signal light L1. The transmission system comprises means 8 for detecting the bit error rate of a received signal which deteriorates as the polarization fluctuates. A feedback signal from the detector is used to change the polarization 3 to an orthogonal polarization state. <IMAGE>
Description
Title of Invention
Signal state of polarization controlling optical transmission system
Background of the invention
The invention relates to such optical communication system equipment as an optical submarine repeater system that encompasses a long-distance optical fiber and a number of optical amplifier repeaters.
As state of polarization in an optical fiber generally changes from moment to moment according to changes in the external environment, the state of polarization of signals in an optical fiber communication system undergo constant changes.
If repeaters using optical amplifiers exist in such a system, the repeater output level would fluctuate because the insertion loss of optical components in the optical amplifiers changes according to the state of polarization of signal light.
The optical amplifier multi-repeater system whose development is now under way merely amplifies light at each repeater to primarily compensate for the attenuation of signal light incurred during transmission. Consequently, said fluctuation in repeater output level accumulates and the ratio of signal light level to optical noise in the system (CNR, or carrier-to-noise ratio in the optical domain) fluctuates to cause a deterioration in the bit error rate characteristic of transmitted signal. This phenomenon becomes more prominent as more repeaters are used in the system.
Once this deterioration in bit error rate characteristic occurs, it cannot be resolved with conventional technology until the state of polarization in the system changes naturally. Therefore, the deterioration in bit error rate characteristic continues for an unpredictable length of time.
In particular, once said deterioration in bit error rate characteristic occurs in an optical submarine cable system, it continues for a long time because there is little change in the system's external environment. Thus, the fluctuation in the state of polarization in the system takes place at an extremely slow pace (e.g., the state indicated in Technical Digest, 29A4-3, IOOC '83, Tokyo 1983). Consequently, the deterioration in bit error rate characteristic has a serious impact on an optical amplifier multi-repeater system, and is one of the principal constraints in realizing the communication system.
One of the ways to reduce this characteristic deterioration in transmission is to minimize the polarization dependence of optical components in each repeater. In a transoceanic optical submarine cable system that extends for several thousand kilometers and encompasses more than 100 repeaters, the tolerable polarization dependence of optical components in each repeater would be far less than 0. 1 dB.
Considering the polarization dependence of calibration apparatus (e.g., approximately 0.5 dB at an optical spectrum analyzer), it is extremely difficult for all practical purposes to construct such repeaters. This has made it difficult to realize an optical amplifier multi-repeater system of several thousand kilometers that maintains a stable bit error rate characteristic for a long time.
The invention resolves promptly after occurrence the deterioration of bit error rate characteristic of received signals caused by changes in the state of polarization of signal lights in an optical amplifier multi-repeater system.
The invention thereby provides a signal state of polarization controlling optical transmission system in an optical amplifier multi-repeater system of several thousand kilometers in length with superior stability in long-term bit error rate characteristic.
Summarv of the invention
The present invention solves said problem by employing the new, unique configuration means described below.
In essence, the first exclusive properties of the present invention comprise at the receiving terminal equipment a means of detecting the deterioration of bit error rate characteristic of received signal light and a means of notifying information on said detected deterioration in bit error rate characteristic to the transmitting terminal equipment, and at the transmitting terminal equipment a signal light source means to output signal light, modulation means to modulate the signal light from said signal light source means, a polarization changing means to change the signal light modulated by said modulation means to an arbitrary state of polarization, and a reception control means to control the signal light from modulation means to an arbitrary state of polarization by receiving information on the deterioration of bit error rate characteristic from said receiving terminal equipment and using said polarization changing means.
The second exclusive properties of the signal state of polarization controlling optical transmission system with said first exclusive properties is that the polarization changing means used in the transmitting terminal equipment is a halfwave plate.
As the invention uses the configuration means described above, when a deterioration is detected in the bit error rate characteristic of signal light received by the receiving terminal equipment, said information on deterioration is transmitted to the transmitting terminal equipment, and the state of polarization of signal light, which is believed to be the primary cause of the characteristic deterioration, is controlled and changed at the transmitting terminal equipment.
DescriPtion of the drawing
Figure 1 is a block diagram of the embodiment example of the invention.
Detailed descrintion of exemplary embodiments
Drawings are used to describe an embodiment of the invention.
Fig. 1 shows the configuration of this embodiment example.
In the figure, d indicates an optical communication system such as a transoceanic optical submarine cable system in whose transmission a number of optical amplifier multi-repeaters are inserted, A is a transmitting terminal equipment, B is a receiving terminal equipment, S is bit error rate characteristic information output from receiving terminal equipment B to transmitting terminal equipment A.
L1 indicates an output signal light from transmitting terminal equipment A to transmission line 7, L2 is an input signal light from transmission line 7 to receiving terminal equipment B, 1 is a signal light source that outputs linearly polarized light, and 2 is an optical modulator that modulates with data signal the signal light from signal light source 1 while maintaining the state of polarization of said signal light.
3 indicates a half-wave plate that changes the state of polarization of the signal light from signal light source 1, 4 is an output optical fiber of transmitting terminal equipment
A, 5 is a collimating lens, and 6 is a reception controlling equipment that receives bit error rate characteristic information S from receiving terminal equipment B and controls halfwave plate 3.
7 indicates transmission line including repeaters using optical amplifiers, 8 is a detecting equipment that detects deterioration in bit error rate characteristic of signal light
L2, and 9 is a transmitting equipment that transmits to transmitting equipment terminal A the detected bit error rate characteristic information S.
The embodiment example presents a specific form of application such as that described above. Described below are the operations of the embodiment example.
The signal light that exits signal light source 1, is modulated with data signal by optical modulator 2, and is input to half-wave plate 3 is a linearly polarized light. The linearly polarized light passes half-wave plate 3 and is output from optical fiber 4 to transmission line 7 as signal light L1.
Signal light L2, after transmission over transmission line 7, is received by receiving terminal equipment B and is demodulated into data signals.
At this moment, if detecting equipment 8 that detects the bit error rate characteristic of received signal light L2 and that is built into the receiving terminal equipment B detects a deterioration in the bit error rate characteristic of received signal light L2 from the standard value, transmitting equipment 9 notifies the bit error rate characteristic information S on received signal light L2 to transmitting equipment A.
When transmitting terminal equipment A receives said information S with reception control equipment 6, transmitting terminal equipment A turns half-wave plate 3 45 degrees to convert the state of polarization of output signal light Lt from transmitting terminal equipment A to a state of polarization that is orthogonal to the previous state of polarization.
In general, the input state of polarization at which the insertion loss of optical components is at maximum and that at which it is at minimum are orthogonal to each other. Therefore, said deterioration in bit error rate characteristic can be eliminated by changing the state of polarization of the transmitting terminal output signal to a state of polarization that is orthogonal to the previous state of polarization when the deterioration in bit error rate characteristic of received signal light L2 was substantial due to the accumulated effect of repeater output fluctuation in transmission line 7.
In essence, by controlling at optical communication system a with transmitting terminal equipment A the state of polarization of signal light L1 input to transmission line 7 including amplification repeaters, the invention is able to improve the accumulating state of output fluctuation of amplification repeaters in the system, and promptly eliminate the deterioration of bit error rate characteristic of transmitted signals due to the accumulated effect of amplification repeater output fluctuation.
Moreover, the rotating angle of half-wave plate 3 may be set to the optimum value according to the bit error rate characteristic information S of received signal light L2 at receiving terminal equipment B by employing a rotating angle step of less than 45 degrees. Half-wave plate 3 also may be rotated until the bit error rate characteristic information S on-received signal light L2 satisfies the standard value. Furthermore, half-wave plate 3 that changes the state of polarization of signal light L1 may be composed of a number of half-wave plates, each of which is able to rotate freely, or of optical components with comparable functions.
As described above, according to this invention, by employing an optical transmitting terminal configuration that changes the state of polarization of output light of transmitting terminal equipment in an optical amplifier multi-repeater system as much as the level of change set in advance, it is possible to promptly eliminate the deterioration in bit error rate characteristic due to the fluctuation of state of polarization of signal light transmitted over transmission in the system. Consequently, because the invention reduces the time span that the bit error rate characteristic deteriorates in an optical amplifier multi-repeater system that had taken place over a longer time span with conventional technology, the invention offers superior utility.
Claims (3)
1. A signal state of polarization controlling optical transmission system for transmitting a signal light, said transmission system is used in an optical communication system that encompasses as repeaters those optical amplifiers whose output signal power fluctuates according to the state of polarization of signal lights, characterized in that said transmission system further comprises at a receiving terminal equipment of said optical communication system:
a detective means for detecting the deterioration in bit error rate characteristic of received signal light; and
a notified means for notifying said detected deterioration in bit error rate characteristic to the transmitting terminal equipment;
said transmission system further comprises at a transmitting terminal equipment of said optical communication system:
a light source means for outputting the signal light;
a modulation means for modulating the signal light from said light source means;
a polarization changing means for changing the signal light modulated by said modulation means to an arbitrary state of polarization; and
a reception controlling means for receiving the bit error rate deterioration information from said receiving terminal equipment and for controlling said polarization changing means in accordance with the bit error rate deterioration information.
2. A signal state of polarization controlling optical transmission system according to the claim 1,
in which said polarization changing means at the transmitting terminal equipment comprises a half-wave plate.
3. A signal state of polarization controlling optical transmission system substantially as hereinbefore described with reference to the accompanying drawing.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4131280A JPH05327626A (en) | 1992-05-25 | 1992-05-25 | Optical communication system device for polarized light state control |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9310665D0 GB9310665D0 (en) | 1993-07-07 |
| GB2267405A true GB2267405A (en) | 1993-12-01 |
| GB2267405B GB2267405B (en) | 1995-08-23 |
Family
ID=15054255
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9310665A Expired - Fee Related GB2267405B (en) | 1992-05-25 | 1993-05-24 | Signal state of polarization controlling optical transmission system |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH05327626A (en) |
| GB (1) | GB2267405B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0660549A1 (en) * | 1993-12-23 | 1995-06-28 | AT&T Corp. | Dual-wavelength data transmitter for reducing fading in an optical transmission system |
| EP0670642A1 (en) * | 1994-02-23 | 1995-09-06 | Canon Kabushiki Kaisha | Light-emitting apparatus capable of selecting polarization direction, optical communication system, and polarization modulation control method |
| US7447441B2 (en) | 2001-12-12 | 2008-11-04 | Ericsson Ab | Signal transmission apparatus and a method of signal transmission |
| US20220390322A1 (en) * | 2021-06-07 | 2022-12-08 | Viavi Solutions Inc. | Techniques for providing a swept wavelength (sw) measurement for acquiring polarization dependent loss (pdl) in a single scan |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5526162A (en) * | 1994-09-27 | 1996-06-11 | At&T Corp. | Synchronous polarization and phase modulation for improved performance of optical transmission systems |
| JP4282559B2 (en) * | 2004-07-14 | 2009-06-24 | 日本電信電話株式会社 | Optical transmission method and optical transmission system |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4968110A (en) * | 1990-01-31 | 1990-11-06 | The United States Of America As Represented By The Secretary Of The Navy | Apparatus and method for optimizing the modulation efficiency of a remotely-located, polarization-sensitive, integrated optic modulator which is addressed with a non-polarization-preserving fiber |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2668399B2 (en) * | 1988-07-14 | 1997-10-27 | 富士通株式会社 | Light output control device |
| JP2540951B2 (en) * | 1989-08-09 | 1996-10-09 | 日本電気株式会社 | Collective polarization control method |
-
1992
- 1992-05-25 JP JP4131280A patent/JPH05327626A/en active Pending
-
1993
- 1993-05-24 GB GB9310665A patent/GB2267405B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4968110A (en) * | 1990-01-31 | 1990-11-06 | The United States Of America As Represented By The Secretary Of The Navy | Apparatus and method for optimizing the modulation efficiency of a remotely-located, polarization-sensitive, integrated optic modulator which is addressed with a non-polarization-preserving fiber |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0660549A1 (en) * | 1993-12-23 | 1995-06-28 | AT&T Corp. | Dual-wavelength data transmitter for reducing fading in an optical transmission system |
| AU701484B2 (en) * | 1993-12-23 | 1999-01-28 | At & T Corporation | Dual-wavelength data transmitter for reducing fading in an optical transmission system |
| EP0670642A1 (en) * | 1994-02-23 | 1995-09-06 | Canon Kabushiki Kaisha | Light-emitting apparatus capable of selecting polarization direction, optical communication system, and polarization modulation control method |
| US5590145A (en) * | 1994-02-23 | 1996-12-31 | Canon Kabushiki Kaisha | Light-emitting apparatus capable of selecting polarization direction, optical communication system, and polarization modulation control method |
| US7447441B2 (en) | 2001-12-12 | 2008-11-04 | Ericsson Ab | Signal transmission apparatus and a method of signal transmission |
| US20220390322A1 (en) * | 2021-06-07 | 2022-12-08 | Viavi Solutions Inc. | Techniques for providing a swept wavelength (sw) measurement for acquiring polarization dependent loss (pdl) in a single scan |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2267405B (en) | 1995-08-23 |
| GB9310665D0 (en) | 1993-07-07 |
| JPH05327626A (en) | 1993-12-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5587830A (en) | High capacity optical fiber network | |
| US5539563A (en) | System and method for simultaneously compensating for chromatic dispersion and self phase modulation in optical fibers | |
| US5491576A (en) | Dual-wavelength data transmitter for reducing fading in an optical transmission system | |
| US6104515A (en) | Method and apparatus for providing high-order polarization mode dispersion compensation using temporal imaging | |
| US6823141B2 (en) | Optical transmission system and dispersion compensator | |
| US7127181B2 (en) | System for mitigating the effects of fiber dispersion by separate detection of two transmitted sidebands | |
| US6671464B1 (en) | Polarization mode dispersion compensator and compensation method | |
| JP2000031900A (en) | Method for optical fiber communication and terminal station device and system used for execution of the method | |
| EP0964538B1 (en) | Optical transmitter and optical transmission system using polarisation modulation | |
| US6647176B1 (en) | Method and apparatus to compensate for polarization mode dispersion | |
| US20090162059A1 (en) | Wavelength division multiplexing transmission system | |
| WO2010043934A1 (en) | Apparatus and method for compensating polarization mode dispersion | |
| CA2363871A1 (en) | Optical transmission system and optical transmission method | |
| WO2002051042A2 (en) | Method and apparatus for suppressing relative intensity noise (rin) and improving transmission signals | |
| US6889347B1 (en) | Automatic configuration and optimization of optical transmission using raw error rate monitoring | |
| GB2267405A (en) | Polarization control in an optical transmission system | |
| US6317240B1 (en) | System for and a method of compensating polarization dispersion in an optical transmission system | |
| US6646774B1 (en) | Intra-bit polarization diversity modulation | |
| Ono et al. | 10 Gb/s PMD compensation field experiment over 452 km using principal state transmission method | |
| US6819877B1 (en) | Optical links | |
| Norimatsu et al. | The influence of cross-phase modulation on optical FDM PSK homodyne transmission systems | |
| CA2423240A1 (en) | Method and apparatus for chromatic dispersion compensation | |
| CA2133132A1 (en) | Technique for improving performance in an optical transmission system | |
| US6542271B1 (en) | Apparatus and method for reducing optical impairments in optical communications systems and networks | |
| Hui et al. | PMD-insensitive SCM optical receiver using polarization diversity |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20040524 |