GB2387222A - Wavelength measurement - Google Patents
Wavelength measurement Download PDFInfo
- Publication number
- GB2387222A GB2387222A GB0207825A GB0207825A GB2387222A GB 2387222 A GB2387222 A GB 2387222A GB 0207825 A GB0207825 A GB 0207825A GB 0207825 A GB0207825 A GB 0207825A GB 2387222 A GB2387222 A GB 2387222A
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- GB
- United Kingdom
- Prior art keywords
- wavelength
- attenuator
- attenuation
- absorption
- signal
- 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.)
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- 238000005259 measurement Methods 0.000 title description 4
- 230000003287 optical effect Effects 0.000 claims abstract description 63
- 238000010521 absorption reaction Methods 0.000 claims abstract description 57
- 238000000034 method Methods 0.000 claims description 25
- 230000001419 dependent effect Effects 0.000 claims description 13
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical group [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 6
- 229910052710 silicon Inorganic materials 0.000 claims description 6
- 239000010703 silicon Substances 0.000 claims description 6
- 239000002800 charge carrier Substances 0.000 claims 2
- 239000002019 doping agent Substances 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 230000008033 biological extinction Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 239000012212 insulator Substances 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- 238000001465 metallisation Methods 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000003094 perturbing effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
Classifications
-
- 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
- G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
- G02B6/266—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting the optical element being an attenuator
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Communication System (AREA)
Abstract
The wavelength of a channel of an optical signal is measured by inputting the signal into a demultiplexer 2, to separate each channel, then directing each channel to an optical absorption attenuator 4 having a optical absorption attenuation characteristic that varies with wavelength in a known manner. The degree of attenuation applied by the attenuator 4 to the signal is measured by measuring the output at a photodiode array 6, and using that and the known attenuation characteristic, the wavelength can be determined. More specifically, an attenuator is used which is switchable between a high attenuating state and a low attenuating state, the ratio of attenuation between the two varying with wavelength.
Description
WAVELENGTH MEASUREMENT
The present invention relates to a method of, and a system for, measuring the wavelength of an optic signal.
Known methods of measuring the wavelength of an optic signal include the method described in co-pending international application no. PCT/GB00/03362.
In this method, the optic signal is directed to an interferometric attenuator whose degree of attenuation varies periodically with wavelength in a known manner, and the wavelength is determined from the measured degree of attenuation.
In OFC 2000, p.168-170, there is described a method of wavelength monitoring in DWDM networks using semiconductor laser diode/amplifers.
It is an aim of the present invention to provide an alternative method of, and device for, measuring the wavelength of an optic signal.
According to a first aspect of the present invention, there is provided a method of measuring the wavelength of an optic signal, including the steps of: inputting the optic signal into an optical absorption attenuator which has an absorption attenuation characteristic that varies with wavelength of the signal in a known manner; measuring the degree of attenuation applied by the attenuator to the signal; and determining the wavelength from the measured degree of attenuation and the absorption attenuation characteristic.
According to another aspect of the present invention, there is provided a method of measuring the wavelength of an optic signal, including the steps of: inputting the signal into an optical device including a variable optical absorption attenuator sNvitchable between a relatively high attenuating state and a relatively low attenuating state, the difference in attenuation of the optical device between the low and high attenuating states varying with the wavelength of the signal in a known manner according to the wavelength-dependent absorption attenuation
characteristic of the variable optical absorption attenuator; switching the attenuator between the low and high attenuating states; measuring the optical power of the signal output from the device for each of the low and high attenuating states, and determining the wavelength of the signal from the difference between the measured optical powers and the absorption attenuation characteristic. According to another aspect of the present invention, there is provided a method of measuring the wavelength of an optic signal, including the steps of: determining the wavelengthdependent characteristic of an optical absorption attenuator; inputting the signal into the optical absorption attenuator; measuring the degree of attenuation applied by the attenuator to the signal; and determining the wavelength from the measured degree of attenuation and the absorption attenuation characteristic.
According to another aspect of the present invention, there is provided a method of measuring the wavelength of at least one channel of a multiplexed signal, including the steps of: inputting the multiplexed signal into a demultiplexer; inputting at least one demultiplexed channel output from the demultiplexer into a respective optical absorption attenuator having an absorption attenuation characteristic that varies with wavelength in a known manner; measuring the degree of attenuation applied by the attenuator to the channel; and determining the wavelength of the at least one channel from the respective degree of attenuation and the attenuation absorption characteristic.
According to another aspect of the present invention, there is provided a method of measuring the wavelength of the channels of a multiplexed signal, including the steps of: providing an optic device including a parallel array of variable optical absorption attenuators each switchable between a relatively high attenuating state and a relatively low attenuating state, the difference in attenuation of the optic device between the low and high attenuating states dependent on wavelength of each channel in a known manner according to the wavelength-dependent
absorption attenuation characteristic of the variable optical absorption attenuators; inputting a multiplexed signal into a demultiplexer; inputting each channel output from the demultiplexer into a respective one of the variable attenuators of the optic device; switching each attenuator between the low and high attenuating states, measuring the optical power of the output from the optic device for each channel for each attenuating state, and determining the wavelength of each channel from the respective difference between the measured optical powers and the absorption attenuation characteristic.
According to another aspect of the present invention, there is provided an optic system including an optic device including a variable optical absorption attenuator switchable between a relatively high attenuating state and a relatively low attenuating state, the difference in attenuation of the optical device between the low and high attenuating states varying with wavelength of the respective channel in a known manner according to the wavelength-dependent absorption attenuation characteristic of the variable optical absorption attenuator; a light detector for measuring the power of the output of the device; and a controller for switching each attenuator between the low and high attenuating states and for determining the wavelength on the basis of the outputs of the light detector and the absorption attenuation characteristic.
According to another aspect of the present invention, there is provided an optic system including a demultiplexer, an optical device including a parallel array of variable optical absorption attenuators for each receiving a respective output channel from the demultiplexer and switchable between a relatively high attenuating state and a relatively low attenuating state, the difference in attenuation of the optical device between the low and high attenuating states varying with wavelength of the respective channel in a known manner according to the wavelength-dependent absorption attenuation characteristic of the variable optical absorption attenuator; at least one light detector for measuring the power of the output of the device for each channel; and a controller for switching each attenuator between the low and high attenuating states and for determining the
wavelength for each channel on the basis of the outputs of the at least one light detector and the absorption attenuation characteristic.
Embodiments of the present invention are described hereunder, by way of non-
limiung example only, with reference to the accompanying drawings, in which: Figure 1 illustrates a device for measuring the wavelength of the channels of a multiplexed signal according to an embodiment of the present invention; Figure 2 illustrates a device for measuring the wavelength of the channels of a multiplexed signal according to another embodiment of the present invention; Figure 3 illustrates in cross- section the basic structure of a p-i-n carrier injection type electronic variable optical attenuator for use in an embodiment of the present invention; Figure 4 shows the wavelength dependence of an electronic variable optical attenuator of the type shown in Figure 3; Figure 5 illustrates an electronic variable optical attenuator for use in an embodiment of the present invention; and Figure 6 illustrates an example of a particular type of p-i-n carrier injection type electronic variable optical attenuator for use in an embodiment of the present Invention. With reference to Figure 1, an optic system according to a first embodiment of the present invention is as follows. A silicon-on-insulator (SOT) chip, whose outline is represented by the dashed line has defined therein a demultiplexer 2, such as an AWG-based demultiplexer, for directing each channel of a wavelength multiplexed signal to a respective one of an array of output rib waveguides 3.
Each of the output waveguides is provided with a respective electronic variable optical attenuator of the type shown in Figures 3 and 5. A photodiode array 6 is provided at the edge of the optic chip where the output waveguides terminate to detect the power of the output from each waveguide. A controller 9 is provided to switch the attenuators between relatively low and high attenuating states, and to compute the wavelength of each channel from the difference in the outputs generated by the respective photodiode for the low and high attenuating states.
Although the AWG-based demultiplexer provides some degree of wavelength discrimination by separating the multiplexed signal into its respective channels, the present invention can be used to precisely determine the centre wavelength of each channel signal.
With reference to Figure 2, an optic system according to a second embodiment of the present invention is as follows. A silicon-on-insulator (SOI) chip, whose outline is represented by the dashed line has defined therein a demultiplexer 2, such as an AWG-based demultiplexer, for directing each channel of a wavelength multiplexed signal to a respective one of an array of waveguides 13. Each of the vaveguides 13 is provided with a respective electronic variable optical attenuator of the type shown in Figures 3 and 5. The waveguides 13 are each connected to.a respective input of a multiplexer, such as an AWG-based multiplexer, to direct each channel to a common output rib waveguide. A photodiode 10 is provided at the edge of the optic chip where the output waveguide 15 terminates to detect the light output from the output waveguide. Alternatively, the multiplexer could be arranged to direct each channel directly to the photodiode at the edge of the chip without the use of an output waveguide. As with the system shown in Figure 1, a controller 9 is provided to switch the attenuators between relatively low and high attenuating states, and to compute the wavelength of each channel from the difference in the outputs generated by the respective diode for the low and high attenuating states. In this case, the EVOAs are also controlled by the controller 9 such that at any given time all but a selected one of the EVOAs are operated in a substantially non- transmitting state to avoid the "unwanted" channels causing a significant error in the wavelength measurement of the single selected channel.
The extinction ratio of the EVOAs for the "unwanted" channels should be over 55dB or the single selected channel should have some form of modulation for a lock-in detection and rejection of unwanted light from "unwanted" channels.
Figure 3 illustrates the basic structure of a p-i-n diode constituting the electronic variable optical attenuators of Figures 1 and 2. A longitudinal rib 17 is defined by
etching trenches into the epitaxial silicon layer 16 overlying the silicon oxide optical confinement layer 14 to form a silicon rib waveguide. Then p and n dopants are introduced into the slab regions 22, 24 either side of the rib vaveguide at a sufficient distance to prevent the dopants perturbing the waveguide mode The n and p type dopants provide ohmic contacts to the silicon and thus form a p-i-n diode. Contact to the doped areas 22, 24 is made using appropriate metallisation 20. An oxide layer 18 electrically insulates the metallisation from other portions of the surface of the epitaxial silicon layer. By forward biasing the diode carriers are injected into the waveguide region.
Electrons and holes are injected in equal proportion in the region of the optical mode, at carrier concentrations in the region of 10'7cm-3 1038cm-3. The use of such a bipolar structure provides a relatively efficient method of carrier injection.
Co-pending GB patent application no. 0104384.3 filed on February 22, 2001 and whose entire content is incorporated by reference describes particular p-i-n diode structures of use in the present invention. One example is shown in Figure 6, wherein in comparison to Figure 3 corresponding components are designated by corresponding numerals. In this example, a pair of trenches 23 are formed either side of the rib and the doping is carried out into these trenches to form n+ and p+ doped areas. By means of these trenches 23, doped areas extending to the lower optical confinement layer 14 can be formed.
In a preferred embodiment, a multiple diode EVOA of the kind shown in Figure 5 is employed. This type of EVOA is described in co-pending UI; application no. 0019771.5, whose content is incorporated herein by reference. Each diode includes an e-type doped region 22 and a p-typed doped region 24 on each lateral side of the rib as shown in Figures 3 and 6. The diodes are in series electrically via metal contacts 30 formed on the surface of the chip to minimise the current consumption of the device. A bias is applied across the EVOA via metallised terminals 26, 28. This type of EVOA can be used to achieve relatively high efficiencies, which is of particular advantage in the embodiment shown in Figure 2 in which the EVOAs are used to achieve relatively high extinctions for switching.
The carrier concentration, and hence the absorption attenuation, is controlled by adjusting the bias across the p-i-n diode. It has been observed that under a given set of operating conditions, the absorption attenuation varies with wavelength, and it is this effect that is exploited in this embodiment.
The wavelength dependence of the absorption attenuation is shown in Figure 4 for six different drive conditions. Over the 100nm bandwidth between 1520 and 1620nm, it is observed that the attenuation is approximately linearly proportional to wavelength. It is also observed that the slope of the linear dependence has a different value for different drive conditions. The difference in the levels of attenuation for two drive conditions therefore also linearly varies with wavelength.
These calibration graphs can be used to determine the wavelength of not only substantially monochromatic signals produced by a laser but also the centre wavelength of, for example, high speed modulated optic signals of the kind used in data transmission.
These calibration graphs were determined as follows. Attenuation levels were fixed at 1570nm by setting the appropriate drive conditions and a tuneable laser was then swept across the C and L wavelength bands whilst measuring the attenuation at a number of known wavelengths.
The relationship between attenuation and wavelength is used to measure wavelength using the devices shown in Figures 1 and 2 in the following manner.
For each of the two devices, a controller is used to switch the electronic variable optical attenuators (EVOA) between two biases for both of which the wavelength-attenuation relationship has been predetermined. In one embodiment, one of the two biases is zero bias at which the wavelength-
dependence of the EVOA attenuation is neglible. The wavelength is determined for each channel from the difference between the respective pair of optical
powers measured by the photodiode at the two biases, and from the wavelength-
attenuation relationships predetermined for each of the two biases.
The wavelength resolution is limited by electrical noise at the photodiode, and this depends on the integration time and the gain of the transimpedance amplifier.
lFor a 10Mohm transimpedance amplifier and monitor photodiode of lnF total capacitance (including external capacitances), a wavelength resolution of approximately 0 73nm may be achieved. If a DSP lock-in algorithm is used to modulate the attenuator current and perform signal processing to effectively increase the detection integration time and reduce electrical noise bandwidth, a wavelength resolution of approximately 0.07nm may be achieved.
The wavelength-dependence of the attenuation of the other optical elements such as the AWG-based demultiplexer and the AWG-based multiplexer in the case of Figure 2 is the same for the two different drive conditions of the EVOA, and hence the difference between the outputs for the two drive conditions is a reflection of the wavelength- dependent absorption characteristic of the electronic variable optical attenuator.
The attenuation characteristic of this type of attenuator is relatively independent of the polarisation of the signal, whereby an accurate measurement of the wavelength can be achieved regardless of the polarisation angle of the signal.
With EVOAs of the kind described above, the absorption exhibits a relatively weak temperature dependence following from the temperature dependence of carrier mobility. In a preferred embodiment, the temperature of the EVOA is maintained to an accuracy of at least + 1oC. This could be implemented with, for example, a thermo-electric cooler.
The applicant draws attention to the fact that the present invention may include any feature or combination of features disclosed herein either implicitly or explicitly or any generalization thereof, without limitation to the scope of any
definitions set out above. In view of the foregoing description it will be evident to
a person skilled in the art that various modifications may be made within the scope of the invention.
Claims (19)
1. A method of measuring the wavelength of an optic signal, including the steps of: inputting the optic signal into an optical absorption attenuator which has an absorption attenuation characteristic that varies \vith wavelength of the signal in a known manner; measuring the degree of attenuation applied by the attenuator to the signal; and determining the wavelength from the measured degree of attenuation and the absorption attenuation characteristic.
2 A method according to claim 1 including the step of measuring the degree of attenuation under a first set of operating conditions relative to that under a different, second set of operating conditions, the difference between the degrees of attenuation at the first and second operating conditions varying with the wavelength of the signal in a known manner.
3. A method according to clatrn 1 or claim 2 wherein the attenuator is a silicon waveguide injected with optically absorbing charge carriers.
4. A method of measuring the wavelength of an optic signal, including the steps of: inputting the signal into an optical device including a variable optical absorption attenuator switchable between a relatively high attenuating state and a relatively low attenuating state, the difference in attenuation of the optical device between the low and high attenuating states varying with the wavelength of the signal in a known manner according to the wavelength-dependent absorption attenuation characteristic of the variable optical absorption attenuator; switching the attenuator between the low and high attenuating states; measuring the optical power of the signal output from the device for each of the low and high attenuating states, and determining the wavelength of the signal from the difference between the measured optical powers and the absorption attenuation characteristic.
5. method according to claim 4 wherein the attenuator is a silicon waveguide injected with optically absorbing charge carriers, whose number is controllably variable to switch the attenuator between the low and high attenuating states.
6. method according to claim 5 wherein the attenuator is an electronic variable optical attenuator.
7. A method of measuring the wavelength of an optic signal, including the steps of: determining the wavelength-dependent characteristic of an optical absorption attenuator; inputting the signal into the optical absorption attenuator; measuring the degree of attenuation applied by the attenuator to the signal; and determining the wavelength from the measured degree of attenuation and the absorption attenuation characteristic.
8. A method according to claim 7, wherein the determination of the wavelength-dependent characteristic is carried out by operating the attenuator under two sets of operating conditions at which the attenuation difference therebetween varies with wavelength; and for each of the two sets of operating conditions inputting light at a plurality of known wavelengths into the attenuator and measuring the attenuation difference for each of the known wavelengths.
9. A method of measuring the wavelength of at least one channel of a multiplexed signal, including the steps of: inputting the multiplexed signal into a demultiplexer; inputting at least one demultiplexed channel output from the demultiplexer into a respective optical absorption attenuator having an absorption attenuation characteristic that varies with wavelength in a known manner; measuring the degree of attenuation applied by the attenuator to the channel; and determining the wavelength of the at least one channel from the respective degree of attenuation and the attenuation absorption characteristic.
10. A method according to claim 9 including the step of measuring the degree of attenuation under a first set of operating conditions of the attenuator relative to that under a different, second set of operating conditions of the attenuator, the difference between the degrees of attenuation at the first and second operating conditions varying with the wavelength of the signal in a known manner.
11. A method of measuring the wavelength of the channels of a multiplexed signal, including the steps of: providing an optic device including a parallel array of variable optical absorption attenuators each switchable between a relatively high attenuating state and a relatively low attenuating state, the difference in attenuation of the optic device between the low and high attenuating states dependent on wavelength of each channel in a known manner according to the wavelength-dependent absorption attenuation characteristic of the variable optical absorption attenuators; inputting a multiplexed signal into a demultiplexer; inputting each channel output from the demultiplexer into a respective one of the variable attenuators of the optic device; switching each attenuator between the low and high attenuating states, measuring the optical power of the output from the optic device for each channel for each attenuating state, and determining the wavelength of each channel from the respective difference between the measured optical powers and the absorption attenuation characteristic.
12. A method according to claim 11 including the step of successively outputting a plurality of channels from the optical device, and directing the output of the optical device to a common light detector whereby the wavelength for the plurality of channels can be determined using a single light detector.
13. A method according to claim 12 wherein each attenuator is switchable into a substantially non-transmitting state, and including the step of controlling the variable attenuators so as to successively output the plurality of channels from the optical device to the common light detector.
14. An optic system including an optic device including a variable optical absorption attenuator switchable between a relatively high attenuating state and a relatively low attenuating state, the difference in attenuation of the optical device between the 1o\v and high attenuating states varying with wavelength of the respective channel in a known manner according to the wavelength-dependent absorption attenuation characteristic of the variable optical absorption attenuator; a light detector for measuring the power of the output of the device; and a controller for switching each attenuator between the low and high attenuating states and for determining the wavelength on the basis of the outputs of the light detector and the absorption attenuation characteristic.
15. An optic system including a demultiplexer, an optical device including a parallel array of variable optical absorption attenuators for each receiving a respective output channel from the demultiplexer and switchable between a relatively high attenuating state and a relatively low attenuating state, the difference in attenuation of the optical device between the low and high attenuating states varying with wavelength of the respective channel in a known manner according to the wavelength-dependent absorption attenuation characteristic of the variable optical absorption attenuator; at least one light detector for measuring the power of the output of the device for each channel; and a controller for switching each attenuator between the low and high attenuating states and for determining the wavelength for each channel on the basis of the outputs of the at least one light detector and the absorption attenuation characteristic.
16. An optic system according to claim 15, wherein the output power of each channel is measured by a respective one of a plurality of light detectors.
17. An optic system according to claim 15, wherein the optic device further includes a multiplexer for receiving the outputs from a plurality of said attenuators and directing them to a common light-detector; and a switch for successively directing the outputs of the attenuators to the multiplexer.
18. An optic system according to claim 17, wherein the attenuators are also switchable to a substantially non-transmitting state, and together also constitute the switch for successively directing the outputs of the attenuators to the multiplexer.
19. An optic system substantially as hereinbefore described with reference to any of Figures 1 and 2 in combination with any of Figures 3 and 5.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0207825A GB2387222A (en) | 2002-04-04 | 2002-04-04 | Wavelength measurement |
| PCT/GB2003/001396 WO2003087742A1 (en) | 2002-04-04 | 2003-03-31 | Wavelength measurement |
| AU2003226524A AU2003226524A1 (en) | 2002-04-04 | 2003-03-31 | Wavelength measurement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0207825A GB2387222A (en) | 2002-04-04 | 2002-04-04 | Wavelength measurement |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0207825D0 GB0207825D0 (en) | 2002-05-15 |
| GB2387222A true GB2387222A (en) | 2003-10-08 |
Family
ID=9934271
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0207825A Withdrawn GB2387222A (en) | 2002-04-04 | 2002-04-04 | Wavelength measurement |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU2003226524A1 (en) |
| GB (1) | GB2387222A (en) |
| WO (1) | WO2003087742A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110149147A (en) * | 2019-07-02 | 2019-08-20 | 易锐光电科技(安徽)有限公司 | A kind of module and implementation method are monitored for wavelength division multiplex transmission networks network medium wavelength |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4027974A (en) * | 1975-12-05 | 1977-06-07 | Bumgardner Jon H | Optical frequency processor |
| GB2168146A (en) * | 1984-12-06 | 1986-06-11 | Stc Plc | Optical wavelength measurement |
| EP0959577A2 (en) * | 1998-05-19 | 1999-11-24 | Nec Corporation | Optical signal repeating and amplifying device and optical level adjusting device |
| US5999271A (en) * | 1998-06-01 | 1999-12-07 | Shih; Ishiang | Methods and devices to determine the wavelength of a laser beam |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2353858A (en) * | 1999-09-01 | 2001-03-07 | Bookham Technology Ltd | Optical wavelength measuring device using integrated optics and photodiodes |
| GB2367142B (en) * | 2000-08-11 | 2003-02-12 | Bookham Technology Plc | An electro optic device |
-
2002
- 2002-04-04 GB GB0207825A patent/GB2387222A/en not_active Withdrawn
-
2003
- 2003-03-31 AU AU2003226524A patent/AU2003226524A1/en not_active Abandoned
- 2003-03-31 WO PCT/GB2003/001396 patent/WO2003087742A1/en not_active Application Discontinuation
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4027974A (en) * | 1975-12-05 | 1977-06-07 | Bumgardner Jon H | Optical frequency processor |
| GB2168146A (en) * | 1984-12-06 | 1986-06-11 | Stc Plc | Optical wavelength measurement |
| EP0959577A2 (en) * | 1998-05-19 | 1999-11-24 | Nec Corporation | Optical signal repeating and amplifying device and optical level adjusting device |
| US5999271A (en) * | 1998-06-01 | 1999-12-07 | Shih; Ishiang | Methods and devices to determine the wavelength of a laser beam |
Also Published As
| Publication number | Publication date |
|---|---|
| AU2003226524A1 (en) | 2003-10-27 |
| WO2003087742A1 (en) | 2003-10-23 |
| GB0207825D0 (en) | 2002-05-15 |
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| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |