WO1987001874A1 - Frequency referencing system and method - Google Patents
Frequency referencing system and method Download PDFInfo
- Publication number
- WO1987001874A1 WO1987001874A1 PCT/GB1986/000553 GB8600553W WO8701874A1 WO 1987001874 A1 WO1987001874 A1 WO 1987001874A1 GB 8600553 W GB8600553 W GB 8600553W WO 8701874 A1 WO8701874 A1 WO 8701874A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- radiation
- filter element
- frequency
- sources
- passbands
- Prior art date
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
- H04B10/501—Structural aspects
- H04B10/506—Multiwavelength transmitters
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
- H01S3/2383—Parallel arrangements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
- H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
-
- 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
- H04B10/572—Wavelength control
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
- H01S5/0687—Stabilising the frequency of the laser
Abstract
A system and method of referencing frequencies of radiation from a plurality of sources, for example lasers (1, 2) includes a filter element (11), such as a Fabry-Perot etalon, onto which the radiation is incident. The filter element has a replicated set of passbands spaced apart in frequency. Detection means (12, 13) detects radiation passing through the filter element (11) and provides corresponding output signals. Control means (16-18, 3, 4) is responsive to the output signals from the detection means (12, 13) to control the sources (1, 2) so that the radiation transmitted through the filter element (11) is maintained substantially constant. The bandwidths of the radiation are small compared with the corresponding passbands of the filter element. The invention is particularly applicable in a communications network in which a number of sets of remote sources of radiation are referenced to a central set of reference sources.
Description
FREQUENCY REFERENCING SYSTEM AND METHOD There is an increasing requirement particularly in optical wideband networks closely to control the wavelength or frequency of the transmitted signals. Indeed, the more channels which are transmitted around the network the more important it is to control the frequency of the signals.
In accordance with one aspect of the present invention, a method of referencing the frequencies of radiation from a plurality of sources comprises guiding the radiation to a filter element having a replicated set of passbands spaced apart in frequency; monitoring radiation transmitted through the filter element; and controlling the sources so that the radiation transmitted through the filter element is maintained substantially constant, the bandwidths of the radiation being smaller than the corresponding passbands of the filter element.
In accordance with a second aspect of the present invention, a frequency referencing system comprises a plurality of sources of radiation of different frequencies; a filter element on to which the radiation is incident, the element having a replicated set of passbands spaced apart in frequency; detection means for detecting radiation passing through the filter element and for providing corresponding output signals; and control means responsive to the output signals from the detection means to control the sources so that the radiation transmitted through the filter element is maintained substantially constant, the bandwidths of the radiation being smaller than the corresponding passbands of the filter element.
The invention provides a particularly simple way to lock the frequencies of the radiation from the sources
relatively to one another. It is thus particularly suitable, when the radiation is optical radiation, in optical wideband networks as described above.
The invention is also applicable to radiation at non-optical frequencies such as radio and microwaves.
The monitoring step may comprise monitoring the intensity of the transmitted radiation. In this case the bandwidths of the radiation are preferably offset from the central frequency of the corresponding passbands of the filter element and particularly conveniently they are positioned close to the edge of the corresponding passbands. The advantage of this is that any change in relative position between the radiation frequency and the filter element passband will correspond with an increase or decrease in the intensity of the radiation transmitted through the filter element depending on the direction of the change.
Alternatively, the phase of the transmitted radiation may be monitored. In this case the radiation bandwidth may be substantially centred on the corresponding passband and any change in the relative positions of the radiation frequency and the passband will result in a phase change in the transmitted beam the type of phase change differing with the direction of movement between the radiation frequency and passband. The advantages of this are that there is no attenuation since the beam is centred on a passband, and any dc drifts will not affect performance since phase and not intensity is monitored. in some cases, the passbands of the filter element will shift together in response for example to temperature changes. Preferably, therefore one source comprises a reference source for generating a reference beam, the method further comprising monitoring transmitted radiation corresponding to the reference
beam, and adjusting the filter element to maintain the transmission characteristic of the reference beam substantially constant. For example, the system may include means for adjusting the filter element in response to output signals from the detection means corresponding to radiation from the reference source.
The adjusting means may comprise means for physically moving or stressing the filter element such as a piezo transducer or a stepper motor or means for adjusting the temperature of the filter element or its support such as a Peltier cooler.
Preferably, the passbands of the filter element are substantially equally spaced apart in frequency.
The filter element may be provided in the case of optical radiation by an optical waveguide loop or ring resonator which passes radiation having the fundamental frequency of the loop and also higher resonant frequencies but is most conveniently provided by a Fabry-Perot etalon. An etalon has a power transfer characteristic, usually at optical frequencies, which exhibits passbands at regular frequency intervals over a wide frequency range. The width of the passbands and their spacing are determined by the mechanical dimensions of the etalon and by the materials and coatings. Etalons may be made for example by using silica glass or air spaced devices. Integrated optic or fibre based devices may be used to achieve a similar effect. The spacing between passbands may range from for example 10 's of MHz to several n . in one example, the radiation from each source may be incident on different parts of the filter element. This enables the different radiation beams to be easily distinguished but requires the use of a corresponding plurality of detectors.
Preferably, therefore, radiation from the plurality of sources is guided along the same path to the filter element, common detection means being provided to receive the radiation transmitted through the filter element, and 5 the control means being arranged to impart respective identifiers to the radiation from each source and to detect from the radiation passing through the filter element each identifer and the radiation corresponding to the identifier.
10. The identifier may comprise a frequency or time code modulation.
Typically, the sources will comprise lasers. In some cases, it may be desirable to provide several sets of sources whose frequencies are referenced
15 to each other, the sets of sources being widely spaced apart physically. The frequencies of these sets of sources could be referenced by providing a reference source whose output is fed to each set of reference sources each of which is provided with its own filter
20 element. However, this requires that each filter element is perfectly matched and in an optical communications network any mismatch could adversely affect switching or transmission performance.
Conveniently, a communications network comprises a
25 frequency reference system in accordance with the second aspect of the invention in which each source of radiation comprises a reference source, multiplexing means for multiplexing the frequency referenced radiation from the reference sources and splitting means for splitting the
30 multiplexed radiation into a plurality of subsidiary signals each of which is fed to a respective set of remote sources of radiation; and subsidiary control means at each set of subsidiary sources for referencing the frequencies of the radiation from the subsidiary sources
35
to one or more of the reference frequencies supplied from the splitting means.
Some examples of systems and methods in accordance with the present invention will now be described with reference to the accompanying drawings which are schematic block diagrams, and in which:-
Figure 1 illustrates one example of the invention; Figure 2 illustrates the transmission characteristics of the filter element shown in Figure 1; Figure 3 illustrates a modification of the example shown in Figure 1;
Figure 4 illustrates a second example; Figure 5 illustrates a third example; and. Figures 6 and 7 illustrate a fourth example. Figure 1 illustrates two lasers 1,2 driven by respective laser drivers 3, 4 which generate optical output signals having bandwidths centered on two different frequencies. The optical signals are guided along optical waveguides 5, 6, such as optical fibres, to respective fibre splitters 7,8. A portion of the signal fed to each splitter 7, 8 is diverted to respective converging lenses 9, 10. Light from the lenses 9, 10 is focussed onto a Fabry-Perot etalon 11 at spaced apart locations. Optical radiation which passes through the etalon 11 is received by respective converging lenses 12, 13 and guided along optical fibres 14, 15 to respective photodiodes 16, 17.
The photodiodes 16, 17 provide electrical outputs corresponding to the intensity of the light passing along the optical fibres 14, 15, the electrical outputs being fed to comparators 18, 19.
The transmission characteristic of the etalon 11 is illustrated in Figure 2. This indicates that the etalon 11 has a plurality of passbands 20 substantially equally
spaced in frequency. The spacing between the passbands 20 may range from 10's of MHz to several nm.
If the output signal from one of the lasers 1,2 has a frequency falling within one of the passbands 20 it will be transmitted through the etalon 11, the intensity of the transmitted signal depending upon the frequency of the signal relative to the passband. In fact, it is preferable if the frequency of the optical signal is not exactly centered within the passband 20 so that any change, in the intensity of the transmitted signal can be correlated easily with the direction of relative movement of the passband and the optical signal frequency.
In an alternative arrangement (not shown) either the laser output is frequency modulated or the etalon frequency spacing is modulated and the photodiodes 16, 17 are followed by phase detectors. In either case, the frequency of the optical signals . may be centred on corresponding passbands and in either case the interaction of the radiation and optical filter causes intensity changes in the received signal. The amplitude of the detected sub-carrier indicates the instantaneous difference between laser frequency and etalon passband and the phase indicates the relative direction of movement. The control of the laser 1 will now be described in detail and it should be understood that similar steps would be carried out to control the laser 2. Initally, a desired output frequency for the optical signal from the laser 1 is set. This output frequency must fall within one of the passbands of the etalon 11 so that in use a signal will be received by the photodetector 17. When the frequency of the optical signal for the laser 1 is at the desired magnitude a reference input to the comparator 19 is set so that the laser driver 3 controls the laser 1 to output an optical signal of the required frequency.
If there is a change in the frequency of the signal from the laser 1 due for example to changes in temperature the signal passing into the waveguide 15 will have a different intensity from its desired value. An electrical signal corresponding to the intensity of the incoming optical signal is generated by the photodiode 17 and is fed to the comparator 19. Since the comparator 19 will detect a difference between the signal from the photodiode 17 and the reference signal it will cause an appropriate electrical signal to be fed to the laser driver 3 to adjust the frequency of the optical signal generated by the laser 1. In this way, the output signal from the laser 1 is maintained at a substantially constant frequency. The laser 2 is similarly controlled but at a frequency corresponding to a different passband of the etalon 11. Since the spacing in frequency between the passbands of the etalon 11 is substantially fixed, the output signals from the lasers 1, 2 will also remain fixed relatively to one another despite changes in te perture or other affects.
For a given etalon, the precise spacings between passbands may vary with temperature. If in Figure 1, temperature changes cause the etalon frequency to shift then, because of the control loops, both lasers 1, 2 will follow the shift and preserve their relative frequency. However, in some applications an absolute stability may be needed which is beyond the stability limits of the etalon. Improved stability may be obtained by means of a control loop in which the angle of the etalon 11 is controlled with respect to the optical axis. This is illustrated in Figure 3. Tilting the etalon 11 in this way causes a slight change in the device optical path length and hence a change in resonant frequency and will
thus restore the passbands of the etalon to their original positions or frequencies.
In this modification, the etalon 11 itself is locked onto a more stable reference such as a HeNe laser 21 or 5 to a laser locked to an atomic reference. As in the Figure 1 example, the optical output signal from the laser 21 is guided to the etalon 11 and the transmitted signal is received by a photodiode 22. This is fed to a comparator 23 whose output is fed to a positional control
ID." unit 24. The positional control unit could be either a piezo transducer of a stepper motor.
A particularly attractive method of stabilising the etalon 11 is to place a crystal of LiNbO, in between the partially reflecting mirrors of the etalon. By
15 controlling the electric field across the LiNbO- the optical pathlength may be varied. This approach would remove the need for mechanical movement of the etalon 11.
The Figure 1 example and indeed its modification require that each optical signal from the lasers is fed
20 to a different part of the etalon 11. This requires that separate photodiodes are provided for each laser. An alternative example which simplifies the construction of the etalon and reduces the number of photodiodes required is illustrated in Figure 4. In this example, a plurality
25 of lasers are provided (only two of which are shown in the drawing) whose output signals are fed to fibre splitters so that a portion of the output signals are guided to an optical combiner 25. The output of the optical combiner 25 is fed to a single converging lens
30 26, through the etalon 11 to a single lens 27 and from the lens 27 to a common photodiode 28. The electrical output from the photodiode 28 is fed to an electrical demultiplexer 29 having one output for each of the lasers.
35
To distinguish between the optical signals from each laser, a modulator 30 is associated with each laser, the modulators 30 imparting a unique identification modulation to the output signals from the lasers. The modulation could be, for example either by frequency or time. If frequency is used then a unique frequency code is allocated to each laser, if time, then a unique time slot or time code is allocated. The electrical demultiplexer 29 senses the identification modulation and provides electrical output signals relating to the intensity of the radiation corresponding to each identification modulation.
Figure 5 illustrates a system for locking a laser to a reference laser based on the Figure 1 example and the modification of Figure 3. A reference laser 31 such as a HeNe laser provides a reference optical signal which is fed to an etalon 32. The output signal from a laser 33 to be referenced is split so that part of the output signal" is also fed to the etalon 32. Optical signals transmitted through the etalon 32 are split with the transmitted reference signal being fed to a photodiode 34 and to a photodiode 35 while the transmitted signal from the laser 33 is fed to a photodiode 36 and to the photodiode 35. The output signal from the photodiode 34 is fed via a buffer 37 and a control interface 38 to a positional control unit 39 similar to that shown in Figure 3. The output from the photodiode 36 is fed via a buffer 40 whose output is split with one portion being fed to a counter 41 and the other portion to a three position switch 42. The output of the photodiode 45 is fed to a filter 43, a comparator 44, and an electrical detector 45 whose output is also fed to the switch 42. The laser 33 is driven by a laser driver 46. Operation of this system is as follows:
1. The position of the etalon 32 is locked so that one of its passbands coincides with the reference frequency from the laser 31. This is achieved using the control loop incorporating the photodiode 34 and
5 the positional control unit 39.
2. With the switch 42 in position (a) , the frequency of the laser 33 is adjusted by adjusting a control A which feeds one input of the comparator 44 so that the laser 33 produces a beat with the
L0- reference signal to produce an electrical IF signal at B. The frequency of the semiconductor laser 33 is now known.
3. The switch 42 is then moved to the position (b) and the semiconductor laser frequency is adjusted to
15 the required wavelength by applying a suitable offset to the laser driver 46. Each time the laser frequency passes through a passband of the etalon
'32, a high level signal appears at C. The counter
41 records the number of times this occurs so that,
20 knowing the frequency of the laser 31 and the passband spacing at the etalon 32, the frequency of the laser 33 is also known.
4. When the required frequency is reached, the switch 42 is set to the position (c) and the laser
25 control loop stabilises the frequency to the required etalon passband as previously described.
In the preceding examples, the reference laser is shown co-sited with the semiconductor lasers being locked. These schemes would also allow the reference
30 laser to be sited remotely from the locked lasers. Several sets of locked lasers might be sited at different locations remote from the reference laser in which case each set could have its own feeder from the reference laser and its own F-P etalon. In these circumstances,
35 unless the etalons were perfectly matched, small
differences in frequency would appear between the locations. In an optical communications network this could adversely affect switching or transmission performance. Figures 6 and 7 illustrate an arrangement to deal with this problem.
The section in dashed lines in Figure 6 corresponds to the Figure 7 example with a majority of the locking system illustrated schematically at 47. The locked signals from the lasers two of which are indicated at 1, 2, with their identification modulations are fed to an optical combiner/splitter 48 so that the optical signals are combined to form an optical frequency multiplex and then transmitted to a number of remote locations. At each location there is provided an optical splitter 49 having one output for each laser of the set of lasers at that location.
Each laser of the set of lasers is connected in an opto-electronic frequency control loop of the form illustrated in Figure 7. The multiplexed reference signals are fed from the splitter 49 along an optical fibre 50 to a photodiode 51, an electrical IF processor 52 and an electrical detector 53. The output from the detector 53 is fed to a buffer 54 whose output is fed to a laser driver 55 which controls the laser 56. The output signal from the laser 56 is split at 57 with a portion of the output signal being fed back to the photodiode 51.
Initially, the loop is locked to any one of the reference signals in the incoming multiplexed signal via the path just described. An electrical beat frequency will appear at the output of the photodiode 51 and this is detected. The detected signal will contain the identification modulation corresponding to the reference frequency with which the laser 56 is locked and this identifier is fed to a code check circuit 58. This
determines in conjunction with a control unit 59 if and how the local laser 56 should be retuned. An appropriate correction signal is then added to the control signal in the buffer 54 to retune the laser 56 to a required channel. When this is completed, control continues via the direct loop path.
ID:
15
20
25
30
35
Claims
1. A method of referencing the frequencies of radiation from a plurality of sources, the method comprising guiding the radiation to a filter element having a replicated set of passbands spaced apart in frequency; monitoring radiation transmitted through the filter element; and controlling the sources so that the radiation transmitted through the filter element is maintained substantially constant, the bandwidths of the radiation being smaller than the corresponding passbands of the filter element.
2. A method according to claim 1, wherein the intensity of the transmitted radiation is monitored, the bandwidths of the radiation being offset from the central frequency of the corresponding passbands of the filter element.
3. A method according to claim 1, wherein either the radiation frequency is modulated or the frequency spacing of the passbands of the filter element is modulated, the amplitude and phase of the detected sub-carrier being monitored.
4. A method according to any of claims 1 to 3, wherein one source comprises a reference source for generating a reference beam, the method further comprising monitoring transmitted radiation corresponding to the reference beam, and adjusting the filter element to maintain the transmission characteristic of the reference beam substantially constant.
5. A method according to any of the preceding claims, further comprising imparting respective identifiers to the radiation from each source; guiding the radiation from each source along a common path to the filter element; detecting from the radiation transmitted through the filter element each identifier; and detecting the radiation corresponding to. the identifiers.
6. A method according to claim 5, wherein the identifier comprises a frequency or time code modulation.
7. A method according to any of the preceding claims, wherein the radiation is optical radiation.
8. A method of referencing the frequencies of radiation from a plurality of sources substantially as hereinbefore described with reference to any of the examples illustrated in the accompanying drawings.
9. A frequency referencing system comprising a plurality of sources of radiation of different frequencies; a filter element on to which the radiation is incident, the element having a replicated set of passbands spaced apart in frequency; detection means for detecting radiation passing through the filter element and for providing corresponding output signals; and control means responsive to the output signals from the defection means to control the sources so that the radiation transmitted through the filter element is maintained substantially constant, the bandwidths of the radiation being smaller than the corresponding passbands of the filter element.
10. A system according to claim 9, wherein one source comprises a reference source the system further including means for adjusting the filter element in response to output signals from the detection means corresponding to radiation from the reference source.
11. A system according to claim 9 or claim 10, wherein the passbands of the filter element are substantially equally spaced apart in frequency.
12. A system according to any of claims 9 to 11, wherein the filter element comprises a Fabry-Perot etalon or a ring resonator.
13. A system according to any of claims 9 to 12, wherein radiation from the plurality of sources is guided along the same path to the filter element, common detection means being provided to receive the radiation transmitted through the filter element, and the control means' being arranged to impart respective identifiers to the radiation from each source and to detect from the radiation passing through the filter element each identifier and the radiation corresponding to the identifier.
14. A system according to any of claims 9 to 13, wherein the sources comprise lasers. - 15. A frequency referencing system substantially as hereinbefore described with reference to any of the examples illustrated in the accompanying drawings. 16. A communications network comprising a frequency referencing system according to any of claims 9 to 15 in which each source of radiation comprises a reference source, multiplexing means for multiplexing the frequency referenced radiation from the reference sources and splitting means for splitting the multiplexed radiation into a plurality of subsidiary signals each of which is fed to a respective set of remote sources of radiation; and subsidiary control means at each set of subsidiary sources for referencing the frequencies of the radiation from the subsidiary sources to one or more of the reference frequencies supplied from the splitting means.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE8686905374T DE3676688D1 (en) | 1985-09-16 | 1986-09-16 | FREQUENCY REFERENCE SYSTEM AND METHOD. |
AT86905374T ATE59503T1 (en) | 1985-09-16 | 1986-09-16 | FREQUENCY REFERENCE SYSTEM AND METHOD. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8522821 | 1985-09-16 | ||
GB858522821A GB8522821D0 (en) | 1985-09-16 | 1985-09-16 | Frequency referencing system |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1987001874A1 true WO1987001874A1 (en) | 1987-03-26 |
Family
ID=10585221
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1986/000553 WO1987001874A1 (en) | 1985-09-16 | 1986-09-16 | Frequency referencing system and method |
Country Status (8)
Country | Link |
---|---|
US (1) | US4839614A (en) |
EP (1) | EP0240512B1 (en) |
JP (1) | JPS63500973A (en) |
CA (1) | CA1251831A (en) |
DE (1) | DE3676688D1 (en) |
ES (1) | ES2002779A6 (en) |
GB (1) | GB8522821D0 (en) |
WO (1) | WO1987001874A1 (en) |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0242802A2 (en) * | 1986-04-17 | 1987-10-28 | Nec Corporation | Optical-wavelength-division multiplex transmission system with an optical filter for spontaneous emission noise |
EP0298598A2 (en) * | 1987-06-09 | 1989-01-11 | AT&T Corp. | Optical communication system with a stabilized group of frequencies |
US4979178A (en) * | 1989-06-20 | 1990-12-18 | The Boeing Company | Tunable narrow-linewidth semiconductor laser |
EP0415645A1 (en) * | 1989-08-31 | 1991-03-06 | AT&T Corp. | Interferometric devices for reducing harmonic distortions in laser communication systems |
EP0426357A2 (en) * | 1989-11-01 | 1991-05-08 | AT&T Corp. | Optical equalization receiver for lightwave communication systems |
EP0474921A1 (en) * | 1990-09-11 | 1992-03-18 | Koninklijke KPN N.V. | Optical transmission network with frequency locking means |
EP0492225A2 (en) * | 1990-12-14 | 1992-07-01 | Firma Carl Zeiss | Device with two laserdiodes for the generation of light with two wavelengths |
WO1996006472A1 (en) * | 1994-08-19 | 1996-02-29 | Leica Ag | Stabilised multi-frequency light source and method of generating synthetic light wavelengths |
GB2293684A (en) * | 1994-09-27 | 1996-04-03 | Northern Telecom Ltd | An interferometric multiplexer,e.g. for an optical amplifier |
GB2305774A (en) * | 1995-09-27 | 1997-04-16 | Nec Corp | A wavelength stability circuit |
WO1998000934A1 (en) * | 1996-06-28 | 1998-01-08 | Alcatel Alsthom Compagnie Generale D'electricite | Optical transmission device for a hybrid fibre-radio system |
Families Citing this family (41)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5039984A (en) * | 1987-10-20 | 1991-08-13 | Telefind Corporation | Paging receiver with programmable areas of reception |
JPH0239131A (en) * | 1988-07-29 | 1990-02-08 | Hitachi Ltd | Method for stabilizing frequency interval and optical heterodyne or optical homodyne communication method |
AT393763B (en) * | 1989-03-21 | 1991-12-10 | Tabarelli Werner | DEVICE FOR CONSISTENCY THE AIR WAVELENGTH OF LASER LIGHT |
US5130998A (en) * | 1990-02-21 | 1992-07-14 | Mitsubiski Denki Kaubshiki Kaisha | Laser device with oscillation wavelength control |
JP2734778B2 (en) * | 1991-01-16 | 1998-04-02 | 日本電気株式会社 | Optical amplifier |
US5408349A (en) * | 1991-07-05 | 1995-04-18 | Hitachi, Ltd. | Optical frequency division multiplexing transmission system |
JPH0576068U (en) * | 1992-03-24 | 1993-10-15 | 横河電機株式会社 | Frequency stabilized light source |
JPH08316938A (en) * | 1995-05-17 | 1996-11-29 | Canon Inc | Optical communication method and optical communication system for multiplexing plural channels |
GB2314617B (en) * | 1996-06-24 | 2000-08-23 | Graviner Ltd Kidde | High sensitivity gas detection |
US5825792A (en) * | 1996-07-11 | 1998-10-20 | Northern Telecom Limited | Wavelength monitoring and control assembly for WDM optical transmission systems |
JPH1075005A (en) * | 1996-08-30 | 1998-03-17 | Ando Electric Co Ltd | Light source device for optical frequency multiplex transmission |
US5978119A (en) * | 1997-02-18 | 1999-11-02 | Lucent Technologies Inc. | System and method for synchronizing an optical source and a router in a wavelength division multiplexed fiber optic network |
US6061158A (en) * | 1997-11-04 | 2000-05-09 | Trw Inc. | High capacity wavelength division multiplexer |
US5956356A (en) * | 1997-12-08 | 1999-09-21 | Lucent Technologies Inc. | Monitoring wavelength of laser devices |
US6370169B1 (en) | 1998-04-22 | 2002-04-09 | Nippon Telegraph & Telephone Corporation | Method and apparatus for controlling optical wavelength based on optical frequency pulling |
WO2000016453A1 (en) | 1998-09-11 | 2000-03-23 | New Focus, Inc. | Tunable laser |
WO2000023764A1 (en) | 1998-10-16 | 2000-04-27 | New Focus, Inc. | Interferometer for optical wavelength monitoring |
ATE359676T1 (en) * | 1999-06-30 | 2007-05-15 | Tno | METHOD AND CODING/DECODING ARRANGEMENT FOR ASSESSING THE IMAGE QUALITY OF REPRODUCED IMAGE DATA |
US6853654B2 (en) * | 1999-07-27 | 2005-02-08 | Intel Corporation | Tunable external cavity laser |
US6879619B1 (en) | 1999-07-27 | 2005-04-12 | Intel Corporation | Method and apparatus for filtering an optical beam |
CA2381662A1 (en) | 1999-08-10 | 2001-02-15 | Reich Watterson | Single etalon optical wavelength reference device |
US6856632B1 (en) | 1999-09-20 | 2005-02-15 | Iolon, Inc. | Widely tunable laser |
US6847661B2 (en) * | 1999-09-20 | 2005-01-25 | Iolon, Inc. | Tunable laser with microactuator |
DE19954036A1 (en) * | 1999-10-29 | 2001-05-10 | Siemens Ag | Wavelength stabilisation method e.g. for optical transmission systems |
US7209498B1 (en) | 2000-05-04 | 2007-04-24 | Intel Corporation | Method and apparatus for tuning a laser |
US6631019B1 (en) | 2000-07-05 | 2003-10-07 | Sri International | Reconfigurable multichannel transmitter for dense wavelength division multiplexing (DWDM) optical communication |
US7120176B2 (en) * | 2000-07-27 | 2006-10-10 | Intel Corporation | Wavelength reference apparatus and method |
US7315697B2 (en) * | 2000-09-26 | 2008-01-01 | Celight, Inc. | Light source for generating an output signal having spaced apart frequencies |
FR2820246B1 (en) * | 2001-01-26 | 2005-06-17 | Algety Telecom | DEVICE AND METHOD FOR SERVING OPTICAL SOURCES |
US6658031B2 (en) | 2001-07-06 | 2003-12-02 | Intel Corporation | Laser apparatus with active thermal tuning of external cavity |
US6822979B2 (en) | 2001-07-06 | 2004-11-23 | Intel Corporation | External cavity laser with continuous tuning of grid generator |
US6901088B2 (en) * | 2001-07-06 | 2005-05-31 | Intel Corporation | External cavity laser apparatus with orthogonal tuning of laser wavelength and cavity optical pathlength |
US6804278B2 (en) | 2001-07-06 | 2004-10-12 | Intel Corporation | Evaluation and adjustment of laser losses according to voltage across gain medium |
US6724797B2 (en) | 2001-07-06 | 2004-04-20 | Intel Corporation | External cavity laser with selective thermal control |
US7230959B2 (en) | 2002-02-22 | 2007-06-12 | Intel Corporation | Tunable laser with magnetically coupled filter |
CA2593989A1 (en) * | 2004-12-16 | 2006-06-22 | Vectronix Ag | Not temperature stabilized pulsed laser diode and all fibre power amplifier |
US20090257460A1 (en) * | 2005-07-13 | 2009-10-15 | Nec Corporation | External resonator variable wavelength laser and its packaging method |
US7583711B2 (en) * | 2006-03-17 | 2009-09-01 | Lockheed Martin Coherent Technologies, Inc. | Apparatus and method for stabilizing the frequency of lasers |
GB2445956B (en) * | 2007-01-26 | 2009-12-02 | Valtion Teknillinen | A spectrometer and a method for controlling the spectrometer |
CN101674135A (en) * | 2008-09-09 | 2010-03-17 | 华为技术有限公司 | Filtering locking method and filtering locking device |
JP5831206B2 (en) * | 2011-12-21 | 2015-12-09 | 富士通株式会社 | Optical switch element, optical demodulator, and optical demodulation method |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4096448A (en) * | 1977-01-12 | 1978-06-20 | Rockwell International Corporation | Phase-locking of independent laser oscillators |
Family Cites Families (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3967211A (en) * | 1974-01-17 | 1976-06-29 | Jersey Nuclear-Avco Isotopes, Inc. | Laser wavelength stabilization |
US4081765A (en) * | 1976-06-03 | 1978-03-28 | Coherent, Inc. | Method and apparatus for providing a calibrated scan for a scanning laser |
US4092070A (en) * | 1976-10-26 | 1978-05-30 | Lansing Research Corporation | Tuning of etalons in spectroscopic apparatus |
US4150342A (en) * | 1977-07-05 | 1979-04-17 | Coherent, Inc. | Method and apparatus for automatically reacquiring a predetermined output radiation frequency in a tunable laser system despite momentary perturbations of laser oscillation |
EP0001714B1 (en) * | 1977-10-26 | 1984-03-21 | The Post Office | Control apparatus for a semi-conductor laser device |
JPS59140B2 (en) * | 1979-01-13 | 1984-01-05 | 日本電信電話株式会社 | semiconductor laser equipment |
GB2043240A (en) * | 1979-03-01 | 1980-10-01 | Post Office | Improvements in or relating to the switching of signals |
US4410992A (en) * | 1980-03-26 | 1983-10-18 | Laser Science, Inc. | Generation of pulsed laser radiation at a finely controlled frequency by transient regerative amplification |
EP0108562A1 (en) * | 1982-11-05 | 1984-05-16 | British Telecommunications | Controlling lasers |
US4672618A (en) * | 1983-03-07 | 1987-06-09 | Beckman Instruments, Inc. | Laser stabilization servo system |
US4592043A (en) * | 1983-07-08 | 1986-05-27 | At&T Bell Laboratories | Wavelength division multiplexing optical communications systems |
US4771431A (en) * | 1985-08-30 | 1988-09-13 | Konishiroku Photo Industry Co., Ltd. | Semiconductor laser drive |
US4719635A (en) * | 1986-02-10 | 1988-01-12 | Rockwell International Corporation | Frequency and phase locking method for laser array |
-
1985
- 1985-09-16 GB GB858522821A patent/GB8522821D0/en active Pending
-
1986
- 1986-09-15 CA CA000518227A patent/CA1251831A/en not_active Expired
- 1986-09-16 WO PCT/GB1986/000553 patent/WO1987001874A1/en active IP Right Grant
- 1986-09-16 EP EP86905374A patent/EP0240512B1/en not_active Expired - Lifetime
- 1986-09-16 ES ES8602290A patent/ES2002779A6/en not_active Expired
- 1986-09-16 DE DE8686905374T patent/DE3676688D1/en not_active Expired - Fee Related
- 1986-09-16 US US07/071,341 patent/US4839614A/en not_active Expired - Lifetime
- 1986-09-16 JP JP61504900A patent/JPS63500973A/en active Granted
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4096448A (en) * | 1977-01-12 | 1978-06-20 | Rockwell International Corporation | Phase-locking of independent laser oscillators |
Non-Patent Citations (4)
Title |
---|
Electronics Letters, Volume 19, No. 16, 4 August 1983, (London GB), C.J. NIELSEN et al.: "New Approach Towards Frequency Stabilisation of Linewidth-Narrowed Se,iconductor Lasers", pages 644-646 see the whole document * |
Electronique et Microelectronique Industrielle, No. 226, 15 October 1976, (Paris, FR), pages 28-31 A. POINSOT et al.: "Realisez un Asservissement de Source Hyperfrequence sur une Cavite Resonnante", pages 28-31 see figure 1; Abstract * |
Japanese Journal of Applied Physics, Volume 20, No. 6, June 1981, (Tokyo, JP), H. TSUCHIDA et al.: "Frequency Stabilization of A1GaAs DH Lasers", pages L403-L406 see figure 4; Abstract * |
Laser und Optoelectronik, Volume 15, No. 3, September 1983, (Stuttgart, DE), G. MEISEL: "Stabilizing and Tuning cw Dye Lasers, Part II", pages 245-251 see figures 2,6,7; page 245, left-hand column, lines 1-25 * |
Cited By (21)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0242802A2 (en) * | 1986-04-17 | 1987-10-28 | Nec Corporation | Optical-wavelength-division multiplex transmission system with an optical filter for spontaneous emission noise |
EP0242802A3 (en) * | 1986-04-17 | 1989-11-08 | Nec Corporation | Optical-wavelength-division multiplex transmission system with an optical filter for spontaneous emission noise |
EP0298598A2 (en) * | 1987-06-09 | 1989-01-11 | AT&T Corp. | Optical communication system with a stabilized group of frequencies |
EP0298598A3 (en) * | 1987-06-09 | 1990-11-22 | American Telephone And Telegraph Company | Optical communication system with a stabilized group of frequencies |
US4979178A (en) * | 1989-06-20 | 1990-12-18 | The Boeing Company | Tunable narrow-linewidth semiconductor laser |
EP0415645A1 (en) * | 1989-08-31 | 1991-03-06 | AT&T Corp. | Interferometric devices for reducing harmonic distortions in laser communication systems |
EP0426357A3 (en) * | 1989-11-01 | 1992-08-12 | American Telephone And Telegraph Company | Optical equalization receiver for lightwave communication systems |
EP0426357A2 (en) * | 1989-11-01 | 1991-05-08 | AT&T Corp. | Optical equalization receiver for lightwave communication systems |
EP0474921A1 (en) * | 1990-09-11 | 1992-03-18 | Koninklijke KPN N.V. | Optical transmission network with frequency locking means |
US5315425A (en) * | 1990-09-11 | 1994-05-24 | Koninklijke Ptt Nederland N.V. | Optical transmission network with frequency locking means |
EP0492225A2 (en) * | 1990-12-14 | 1992-07-01 | Firma Carl Zeiss | Device with two laserdiodes for the generation of light with two wavelengths |
EP0492225A3 (en) * | 1990-12-14 | 1992-07-08 | Firma Carl Zeiss | Device with two laserdiodes for the generation of light with two wavelengths |
US5189677A (en) * | 1990-12-14 | 1993-02-23 | Carl-Zeiss-Stiftung | Arrangement having two laser diodes for generating light having two wavelengths |
WO1996006472A1 (en) * | 1994-08-19 | 1996-02-29 | Leica Ag | Stabilised multi-frequency light source and method of generating synthetic light wavelengths |
US5781334A (en) * | 1994-08-19 | 1998-07-14 | Leica Ag | Stabilized multi-frequency light source and method of generating synthetic light wavelengths |
GB2293684A (en) * | 1994-09-27 | 1996-04-03 | Northern Telecom Ltd | An interferometric multiplexer,e.g. for an optical amplifier |
GB2293684B (en) * | 1994-09-27 | 1998-10-14 | Northern Telecom Ltd | An interfermetric multiplexer |
GB2305774A (en) * | 1995-09-27 | 1997-04-16 | Nec Corp | A wavelength stability circuit |
GB2305774B (en) * | 1995-09-27 | 1997-12-24 | Nec Corp | A wavelength stability circuit |
US5861975A (en) * | 1995-09-27 | 1999-01-19 | Nec Corporation | Wavelength stability circuit |
WO1998000934A1 (en) * | 1996-06-28 | 1998-01-08 | Alcatel Alsthom Compagnie Generale D'electricite | Optical transmission device for a hybrid fibre-radio system |
Also Published As
Publication number | Publication date |
---|---|
EP0240512A1 (en) | 1987-10-14 |
GB8522821D0 (en) | 1985-10-23 |
EP0240512B1 (en) | 1990-12-27 |
DE3676688D1 (en) | 1991-02-07 |
ES2002779A6 (en) | 1988-10-01 |
US4839614A (en) | 1989-06-13 |
CA1251831A (en) | 1989-03-28 |
JPH0553314B2 (en) | 1993-08-09 |
JPS63500973A (en) | 1988-04-07 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP0240512B1 (en) | Frequency referencing system and method | |
US5173794A (en) | Wavelength division multiplexing using a tunable acousto-optic filter | |
US6120190A (en) | Spatially variable bandpass filter monitoring and feedback control of laser wavelength especially in wavelength division multiplexing communication systems | |
US5943152A (en) | Laser wavelength control device | |
US5408349A (en) | Optical frequency division multiplexing transmission system | |
KR100600935B1 (en) | Wavelength control using dither modulation and feedback | |
US6034799A (en) | Tuning source for lightwave systems | |
US5828689A (en) | Etalon arrangement | |
US5469288A (en) | Optical filter, method of controlling transmission wavelength thereof, and optical receiver using the method | |
US6349103B1 (en) | Cold-start wavelength-division-multiplexed optical transmission system | |
US6498871B1 (en) | Wavelength stabilized light source | |
EP0396371B1 (en) | Random-access digitally-tuned optical frequency synthesizer | |
JPH10213830A (en) | Optical reference frequency generating device, optical reference comb generating device, and coherent receiving device | |
US6584245B1 (en) | High speed data link including a superconductive plate assembly for use in a data transmission scheme and method | |
CA2176682C (en) | Optical communication method for performing communication using a plurality of wavelengths, and optical communication system for performing communication using a plurality of wavelengths | |
US6816517B2 (en) | Micro-electromechanical devices for wavelength tunable lasers | |
EP0208729B1 (en) | Optical networks | |
CA2164073C (en) | Transmission wavelength control method permitting efficient wavelength multiplexing, optical communication method, optical transmitter, optical transmitter-receiver apparatus, andoptical communication system | |
US20020154662A1 (en) | Method and apparatus for precision wavelength stabilization in fiber optic communication systems using an optical tapped delay line | |
JPH02140028A (en) | Multiplex wavelength optical communication system | |
US6927377B2 (en) | Wavelength locking channel monitor | |
WO2011029478A1 (en) | Operating a laser in an optical component | |
JPH06188832A (en) | Remote optical terminal control method | |
JPH02228831A (en) | Optical network communication system | |
US20020057476A1 (en) | Collective detection method and detection system for wavelength fluctuations in wavelength division multiplexing optical communication system, and wavelength division multiplexing optical transmission apparatus equipped with this detection system |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AK | Designated states |
Kind code of ref document: A1 Designated state(s): JP US |
|
AL | Designated countries for regional patents |
Kind code of ref document: A1 Designated state(s): AT BE CH DE FR GB IT LU NL SE |
|
WWE | Wipo information: entry into national phase |
Ref document number: 1986905374 Country of ref document: EP |
|
WWP | Wipo information: published in national office |
Ref document number: 1986905374 Country of ref document: EP |
|
WWG | Wipo information: grant in national office |
Ref document number: 1986905374 Country of ref document: EP |