WO1996031961A1 - Dispositif de compensation de la dispersion chromatique - Google Patents
Dispositif de compensation de la dispersion chromatique Download PDFInfo
- Publication number
- WO1996031961A1 WO1996031961A1 PCT/CA1996/000201 CA9600201W WO9631961A1 WO 1996031961 A1 WO1996031961 A1 WO 1996031961A1 CA 9600201 W CA9600201 W CA 9600201W WO 9631961 A1 WO9631961 A1 WO 9631961A1
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- WO
- WIPO (PCT)
- Prior art keywords
- mirror
- port
- etalon
- mirrors
- input
- Prior art date
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- 239000006185 dispersion Substances 0.000 title claims abstract description 28
- BJQHLKABXJIVAM-UHFFFAOYSA-N bis(2-ethylhexyl) phthalate Chemical class CCCCC(CC)COC(=O)C1=CC=CC=C1C(=O)OCC(CC)CCCC BJQHLKABXJIVAM-UHFFFAOYSA-N 0.000 claims abstract description 47
- 238000012544 monitoring process Methods 0.000 claims abstract description 31
- 238000002310 reflectometry Methods 0.000 claims description 23
- 230000003287 optical effect Effects 0.000 claims description 19
- 238000001514 detection method Methods 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims 1
- 239000000463 material Substances 0.000 claims 1
- 239000000835 fiber Substances 0.000 description 13
- 239000013307 optical fiber Substances 0.000 description 8
- 230000005540 biological transmission Effects 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 4
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- 230000003595 spectral effect Effects 0.000 description 1
- 239000012780 transparent material Substances 0.000 description 1
Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/29392—Controlling dispersion
- G02B6/29394—Compensating wavelength dispersion
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
- G02B6/29358—Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator
-
- 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
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
- H04B10/2513—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion
- H04B10/25133—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion including a lumped electrical or optical dispersion compensator
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B2210/00—Indexing scheme relating to optical transmission systems
- H04B2210/25—Distortion or dispersion compensation
- H04B2210/252—Distortion or dispersion compensation after the transmission line, i.e. post-compensation
Definitions
- This invention relates generally to a device for compensation of chromatic dispersion in optical fibers.
- any medium capable of providing a sufficient dispersion opposite to that of the optical fiber can serve as an optical pulse equalizer.
- a special optical fiber having an equal chromatic dispersion at a required operating wavelength but opposite in sign to that of the transmitting fiber can serve as an optical pulse equalizer.
- Other methods include the use of chi ⁇ ed fiber Bragg gratings, and the use of planar lightwave circuit (PLC) delay equalizers.
- PLC planar lightwave circuit
- special compensating fiber has a very high insertion loss and in many applications is not a preferable choice.
- Fiber gratings are generally not practical for field applications due to their narrow bandwidth, and fixed wavelength.
- PLCs are also narrow band, although tunable devices; fabricating a PLC with large dispersion equalization remains to be difficult.
- Cimini L.J. et al. describe an optical equalizer capable of combating the effects of laser chi ⁇ and fiber chromatic dispersion on high-speed long-haul fiber-optic communications links at 1.55 ⁇ m. Also discussed is a control scheme for adaptively positioning the equalizer response frequency. Cimini et al. describe a device having only one common input/output port at a first partially reflective mirror and a second 100% reflective mirror together forming a cavity. The control scheme described attempts to track signal wavelength by obtaining feedback from a receiver. The amplitude response of the equalizer is essentially flat with wavelength at the input/output port, and thus, the proposed control scheme is somewhat complex requiring processing of high speed data at the optical receiver.
- the proposed control method is stated to function with RZ signals but not with NRZ signals, a more commonly used data format.
- the equalizer described by Cimini et al. appears to perform its intended basic dispersion compensating function, there exists a need for an improved method of control of the position of the equalizer frequency response, and as well, there exists a need for an equalizer that will provide a sufficient time shift over a broader range of wavelengths.
- a device for dispersion compensation comprising an etalon having first and second partially reflective mirrors in a parallel spaced relationship to form a gap between the mirrors, the first partially reflective mirror being substantially less reflective than the second mirror to allow substantially most of an input signal to pass through the first partially reflective mirror, the first mirror having an input/output port for providing the input signal to the gap between the mirrors, the second mirror having at least a region thereof that allows a substantially small amount of the input signal to pass therethrough for providing a monitoring port, said monitoring port being substantially optically aligned with said input port.
- a two port device for dispersion compensation comprising: a first partially reflective mirror; a second partially reflective mirror having a substantially greater reflectivity than the first mirror, the first and second mirrors being in a parallel spaced relationship defining an optical cavity, first mirror having a single input/output port and the second mirror having a single output monitoring port substantially axially aligned with the first input/output port.
- a device for dispersion compensation comprising: at least two etalons, a first of the two etalons having first and second reflective mirrors in a parallel spaced relationship, to form a gap between the mirrors, the first mirror being partially reflective and having a predetermined reflectivity to allow an input signal to pass therethrough to the gap between the parallel mirrors, and a second etalon, the second etalon having a first mirror and second mirror, said first mirror having a predetermined reflectivity that is dissimilar from the reflectivity of the first reflective mirror, the first and second mirrors of the second etalon being in a parallel spaced relationship to form a gap between the mirrors, the first and second etalons being arranged in series so that most of a signal launched into the first etalon later propagates into the second etalon after traversing the first etalon.
- the invention provides a device with a monitor port on the transmitted side of the etalon. Furthermore, the amplitude response of the monitor (transmitted) port provides a much higher signal contrast ratio (on/off ratio or extinction ratio), than the output (reflected) port.
- a relatively simple, local, control scheme can be implemented, obviating the more complex high speed detection and signal processing schemes suggested in the prior art.
- Another advantage of this invention is that the local control scheme allows the compensation device (etalon) to be located virtually anywhere in the system, even at the transmitter end.
- Fig. 1 is a schematic illustration of a prior art single port dispersion equalization device:
- Fig. 2 is a schematic illustration of a two port dispersion equalization device in accordance with this invention.
- Fig. 3 is graph of time delay versus optical frequency illustrating the response of the equalizer shown in Fig. 2;
- Fig. 4 is a block diagram of a two port equalizer in accordance with this invention having a piezo-electric actuator for adjusting cavity length;
- Fig. 5 is a graph showing the output response of two equalizers; superimposed on the graph is straight line showing the dispersion in an optical fiber as a function of frequency, and the combined response of the two equalizers including optical fiber;
- Fig. 6 is schematic illustration an alternative embodiment showing a two stage cascaded equalizer;
- Fig. 7 is a graph showing the output response for the two stage equalizer of Fig. 6;
- Fig. 8 is schematic illustration of an alternative embodiment of an equalizer having 3 ports: and.
- Fig. 9 is a pictorial side view of a block of solid transparent material coated on opposite end faces with a reflective coating forming a two port etalon.
- a dispersion compensation equalizer 10 having reflective Fabry-Per ⁇ t (FP) etalon having a first partially reflective mirror 12 spaced apart and parallel with a 100% reflective second mirror 14 shown.
- the first mirror provides a single input/output port 13 to allow light to be launched into and out of the cavity defined by the mirrors 12 and 14.
- the equalizer is described by Cimini et al. as an "all pass" network whose amplitude response is flat and whose phase response is designed to counter the effect of the transmission fiber ' s quadratic phase response. Since the amplitude response is flat, it very difficult to extract information from a signal on return from the cavity for use as control signal for cavity adjustment.
- a 3-dB coupler shown
- a polarization independent optical circulator not shown
- a coupler would result in about 6dB of round-trip loss while a circulator would result in about 3dB of loss.
- the power reflectivity of the front mirror is r 2 ;
- T is the round-trip delay of the single cavity: and
- A( ⁇ 1) is constant representing the all-pass loss of the particular structure.
- the first mirror has an input output port 1 13 for porting light into and out of the cavity formed by the mirrors.
- the second mirror 1 14 includes at least a region where the reflectivity is less than 100%; this region provides an output port 1 16 to allow a small amount of the light energy to be to be ported out of the cavity.
- coupling means in the form of a lens or photodetector 1 17 may be provided for coupling light out of the port 116.
- the output port 1 16 be at least optically aligned with the input/output port where light enters the cavity.
- the output port 116 can be used for a variety of pu ⁇ oses, for example, monitoring the presence or absence of energy within the cavity; more importantly the transmitted signal appearing at the output port 116 can be monitored and utilized for locking to and tracking the frequency of the transmitting laser.
- the spectral response of the transmitted signal at the monitor port is periodic in behaviour; thus the amplitude of the monitor output signal varies with wavelength in a periodic manner.
- Control circuitry can change the round-trip delay time between the mirrors by adjusting the cavity length in dependence upon the laser frequency. For example if the frequency of the transmitting laser varies or drifts, the cavity can be dynamically tuned. Referring now to Fig.
- an FP etalon 140 having a piezo electric actuator 144 for adjusting the cavity length between the first and second mirrors 1 12 and 1 14.
- a lens 147 couples a fiber 148 to the etalon
- the piezo electric actuator can be controlled in dependence upon a characteristic of a signal monitored at the output monitor port.
- the monitor signal power varies substantially with wavelength and its value depends upon how near the signal wavelength is to the resonant wavelength of the cavity. Having the option of direct monitoring of the signal at port 1 16, allows the equalizer 100 to be located virtually anywhere in the system. By locating the equalizer 100 near or at the transmitter, a precompensation scheme can be employed and. for example, noise and non-linear effects of fiber can be minimized when an optical fiber amplifier is also deployed in the system. Furthermore, and perhaps more importantly, the monitor (feedback) signal may be utilized to control the transmitting laser, thus locking the transmitter wavelength to the optimum operating wavelength of the equalizer 100.
- Fig. 3 the output response is shown for the equalizer 100; the graph illustrates frequency response of time delay in picoseconds.
- the approximately 5 Ghz bandwidth portion of the response indicated by the two-headed arrow demarks the desired operating region of the filter which counteracts the dispersion in the same optical frequency range. This is more clearly illustrated in the graph of Fig. 5.
- the straight, dotted line shows time delay over a 20 Ghz frequency band (with a negative slope) due to dispersion in an optical fiber after 100 Km transmission.
- the preferred operating regions of the filter shown heretofore in accordance with this invention is limited in bandwidth.
- the operating region of the filter i.e. the positive sloped portion of the equalizer ' s response, is limited to a 5 Ghz bandwidth. Of course, it would be preferable to be able to extend this region without a negative trade-off in relative time delay.
- An etalon equalizer 160 in accordance with this invention having two dissimilar cascaded etalons 162 and 164 is shown in Fig. 6.
- the output response for each of the etalons 162 and 164 and the output response for the cascaded equalizer 160 is shown in Fig. 7.
- the operating wavelength is doubled from 5 to 10 Ghz and the time delay is increased by about 25 percent.
- the nominal distance "d" between first and second mirrors in each cavity is 2 mm. As is shown in Fig. 7. the offset of the center operating wavelength of each of the cavities is approximately 5 Ghz which corresponds to a small difference in cavity spacing (d, ⁇ d 2 ).
- a monitoring port on at least one of the second mirrors of one of the cavities, similar to the monitoring port described earlier. Of course more than two dissimilar stages can be cascaded to provide an equalizer with particular operating characteristics.
- a single stage device 180 (or cascaded multistage device) is provided having separate input and output ports 182 and 184 respectively, on the first mirror 186 of the cavity.
- a single stage device 180 or cascaded multistage device
- the first partially reflective mirror By providing separate and input output ports 182 and 184 at the first partially reflective mirror, light is coupled into and out of the equalizer with considerably less signal power loss than with the 3-dB coupler or a polarization optical circulator proposed by Cimini et al. in the prior art.
- the fold angle 189 at the second mirror 188 between the input port and output port it is necessary for the fold angle 189 at the second mirror 188 between the input port and output port to be small, and nearly equal to but greater than zero degrees.
- a monitoring port 187 is preferably provided at the second mirror to provide signal for use in controlling the cavity.
- etalon 190 in the form of a transparent block of glass 198 is shown having a first partially reflective coating 192 and a second coating 196 spaced apart in a parallel with the first reflective coating 192 on opposite end faces of the block 198.
- the cavity may be filled with air.
- liquid, or as shown in the embodiment of Fig. 9. may be a transparent solid material having reflecting surfaces at opposite ends.
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Lasers (AREA)
- Mechanical Light Control Or Optical Switches (AREA)
- Optical Communication System (AREA)
Abstract
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU52632/96A AU5263296A (en) | 1995-04-05 | 1996-04-03 | Chromatic dispersion compensation device |
JP8529816A JPH11511862A (ja) | 1995-04-05 | 1996-04-03 | 色分散補償装置 |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA2,146,384 | 1995-04-05 | ||
CA 2146384 CA2146384C (fr) | 1995-04-05 | 1995-04-05 | Dispositif servant a compenser la dispersion chromatique |
US08/442,367 | 1995-05-16 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1996031961A1 true WO1996031961A1 (fr) | 1996-10-10 |
Family
ID=4155585
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/CA1996/000201 WO1996031961A1 (fr) | 1995-04-05 | 1996-04-03 | Dispositif de compensation de la dispersion chromatique |
Country Status (2)
Country | Link |
---|---|
CA (1) | CA2146384C (fr) |
WO (1) | WO1996031961A1 (fr) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0897547A4 (fr) * | 1997-02-07 | 2003-07-30 | Fujitsu Ltd | Dispositif optique mettant en oeuvre un groupement en phase et a formation d'images virtuelles, aux fins de production d'une dispersion chromatique |
EP1333309A3 (fr) * | 2002-01-16 | 2004-12-08 | Fujitsu Limited | Compensateur de dispersion à bande passante en transmission aplatie |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN114449237B (zh) * | 2020-10-31 | 2023-09-29 | 华为技术有限公司 | 一种反畸变反色散的方法以及相关设备 |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0426357A2 (fr) * | 1989-11-01 | 1991-05-08 | AT&T Corp. | Récepteur optique à égalisation pour système de communication par ondes optiques |
-
1995
- 1995-04-05 CA CA 2146384 patent/CA2146384C/fr not_active Expired - Fee Related
-
1996
- 1996-04-03 WO PCT/CA1996/000201 patent/WO1996031961A1/fr active Application Filing
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0426357A2 (fr) * | 1989-11-01 | 1991-05-08 | AT&T Corp. | Récepteur optique à égalisation pour système de communication par ondes optiques |
Non-Patent Citations (2)
Title |
---|
CIMINI ET AL: "Optical equalization to combat the effects of laser chirp and fiber dispersion", JOURNAL OF LIGHTWAVE TECHNOLOGY, vol. 8, no. 5, May 1990 (1990-05-01), NEW YORK US, pages 649 - 659, XP000125357 * |
FUJII ET AL: "Nonlinear separation of optical pulses", 12TH EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION, vol. 1, September 1986 (1986-09-01), BARCELONA, SPAIN, pages 209 - 212, XP002008896 * |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0897547A4 (fr) * | 1997-02-07 | 2003-07-30 | Fujitsu Ltd | Dispositif optique mettant en oeuvre un groupement en phase et a formation d'images virtuelles, aux fins de production d'une dispersion chromatique |
JP3516165B2 (ja) | 1997-02-07 | 2004-04-05 | 富士通株式会社 | 色分散を生成するためのバーチャル・イメージ・フェーズ・アレイを用いる光装置 |
EP1333309A3 (fr) * | 2002-01-16 | 2004-12-08 | Fujitsu Limited | Compensateur de dispersion à bande passante en transmission aplatie |
US6909537B2 (en) | 2002-01-16 | 2005-06-21 | Fujitsu Limited | Dispersion compensator whose transmission band is flattened |
Also Published As
Publication number | Publication date |
---|---|
CA2146384A1 (fr) | 1996-10-06 |
CA2146384C (fr) | 1999-05-11 |
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