GB2288013A - Optical wavelength meter - Google Patents
Optical wavelength meter Download PDFInfo
- Publication number
- GB2288013A GB2288013A GB9304091A GB9304091A GB2288013A GB 2288013 A GB2288013 A GB 2288013A GB 9304091 A GB9304091 A GB 9304091A GB 9304091 A GB9304091 A GB 9304091A GB 2288013 A GB2288013 A GB 2288013A
- Authority
- GB
- United Kingdom
- Prior art keywords
- wavelength
- coupler
- output
- wavelength meter
- meter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- 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
-
- 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
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
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- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Optical Communication System (AREA)
Abstract
Fused optical fibre couplers exhibit wavelength-sensitive coupling ratios and can provide wavelength-sensitive gradients of the coupling ratios of opposite signs. The couplers can be used to provide an optical wavelength meter. Additionally, the arrangement can be used to provide a high sensitivity optical power meter. Two such couplers may be cascaded as shown, and the wavelength determined from a comparison of the respective output powers P1, P2 detected by photodiodes 1, 2, or from the ratios P1/P2. The absolute values of P1, P2 may be used to determine the input power. <IMAGE>
Description
WAVELENGTH METER
A low-cost transmissive wavelength meter capable of also working as a transmissive self-adjusting optical power meter is described. The device is fibre based and is suitable for, but not restricted to, use in both telecommunications optical transmission windows.
According to the present invention there is provided a wavelength meter for an optical signal, comprising first and second fused optical fibre couplers, an output of the first coupler being connected to an input of the second coupler, a further output of the first coupler and an output of the second coupler each being connected to a respective photo sensitive device, the wavelength sensitive gradients of the coupling ratios of the outputs being of opposite sign, and the outputs of the photo sensitive devices being connected to a signal processing device, the output of said device being related to the wavelength of a signal input to the wavelength meter.
There is further provided a wavelength meter for an optical signal5 comprising a fused coupler having at least two outputs each output being connected to a respective photo sensitive device, the wavelength sensitive gradients of the coupling ratios of the two outputs being of opposite sign, and the outputs of the photo sensitive devices being connected to a signal processing device, the output of said device being related to the wavelength of a signal input to the wavelength meter.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figures 1(a) - 1(c) show the spectral characteristics with varying coupling ratios for fused fibre couplers, Figure 2 shows diagrammatically one embodiment of a wavelength meter according to the present invention;
Figure 3 is a graph showing an example of a wavelength meter characteristic;
Figure 4 shows diagrammatically a further embodiment of a wavelength meter according to the present invention.
The fibre based wavelength meter described in a first embodiment employs two fused fibre couplers and exploits the wavelength sensitive coupling ratios of the couplers. It was observed that fused fibre couplers' sensitivity increases as the wavelength decreases. The spectral characteristics of three fused fibre couplers of coupling ratios 50%, 10% and 2% (specified at 1550nm) were measured in terms of the optical powers P1 and P2 emerging from each of the couplers' output parts and are shown in
Figure 1. The changes in the coupling ratios over 50nm are ldB, 2dB and 8dB respectively for the 50%, 10% and 2% couplers.
By cascading two such couplers together as shown in
Figure 2, the wavelength of a signal passing through them can be determined by comparing the output powers at the two ports (P1 and P2) or by the ratios P1/P2.
In conjunction with the ratio P1/P2 or the optical wavelength derived from this ratio, the absolute values of P1 and P2 may be employed to determine the power of the applied optical signal, independent of its wavelength.
A further input to the first coupler (as shown in Figures 2 and 4) or the second coupler may be used to provide an additional high sensitivity optical power measurement, as the substantial majority of the applied optical signal is thus directly coupled to a photo sensitive device. The wavelength dependence of the coupler in this event is small.
The performance of a wavelength meter constructed with two couplers of 10% and 2% coupling ratios was measured. From the measurements obtained in Figure 1, it is expected the wavelength meter should be able to give 10dB variation in the ratios P1/P2 over 50nm of wavelength changes.
A tunable External Cavity Laser (ECL) whose wavelength varied from 1532nm to 1582nm was used as the signal source. A dual-head sensor optical power meter was used to measure the powers P1 and P2. The signal wavelength was measured with an optical spectrum analyser. The result is plotted in Figure 3. Over the wavelength range of 50nm, the result can be approximated by a straight line. About 10dB of variation in the ratios P1/P2 over 50nm of wavelength changes was measured.
A separate measurement using a Distributed Feedback (DFB) laser was also performed. No variation in the P1/P2 ratios was observed (that is better than +/-0.005dB). When the signal power was varied by about 18dB (-12dBm to -30dBm), the ratios changed by 0.05dB. This result, however, is repeatable and can therefore be calibrated to allow for the power variation. This variation could be due to the linearity of the optical sensors of the optical power meter. These results indicated that a wavelength meter with the capability of measuring wavelength with a resolution of better than 0.5nm could be constructed using such an arrangement.
Claims (9)
1. A wavelength meter for an optical signal, comprising first and second fused optical fibre couplers, an output of the first coupler being connected to an input of the second coupler, a further output of the first coupler and an output of the second coupler each being connected to a respective photo sensitive device, the wavelength sensitive gradients of the coupling ratios of the outputs being of opposite sign, and the outputs of the photo sensitive devices being connected to a signal processing device, the output of said device being related to the wavelength of a signal input to the wavelength meter.
2. A wavelength meter for an optical signal, comprising a fused optical fibre coupler having at least two outputs each output being connected to a respective photo sensitive device, the wavelength sensitive gradients of the coupling ratios of the two outputs being of opposite sign, and the outputs of the photo sensitive devices being connected to a signal processing device, the output of the said device being related to the wavelength of a signal input to the wavelength meter.
3. A wavelength meter as claimed in Claim 1 or 2, wherein the said device comprises an analogue/digital converter, a microcontroller and memory for storing the relationships between wavelength sensitivities of the couplers and the photo sensitive devices.
4. A wavelength meter as claimed in Claim 1, 2 or 3 further including a means for displaying the wavelength of a signal input to the wavelength meter.
5. A wavelength meter as claimed in Claim 1, 2, 3 or 4 further including display means for displaying the power of a signal input to the wavelength meter.
6. A wavelength meter as claimed in Claim 1, or any claim appendent thereto, wherein the further output of the first coupler and the output of the second coupler have outputs of 10% or less of the signal input to the couplers.
7. A wavelength meter as claimed in Claim 1 or any claim appendent thereto, wherein the further output of the first coupler and the output of the second coupler have outputs of 2% or less of the signal input to the couplers.
8. A wavelength meter as claimed in Claim 6 or 7, wherein a further input of the first or second coupler is provided to channel the substantial majority of the input to a photo sensitive device.
9. A wavelength meter substantially as hereinbefore described5 with reference to and as illustrated in the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9304091A GB2288013B (en) | 1993-03-01 | 1993-03-01 | Wavelength meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9304091A GB2288013B (en) | 1993-03-01 | 1993-03-01 | Wavelength meter |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9304091D0 GB9304091D0 (en) | 1993-04-14 |
| GB2288013A true GB2288013A (en) | 1995-10-04 |
| GB2288013B GB2288013B (en) | 1996-06-19 |
Family
ID=10731228
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9304091A Expired - Fee Related GB2288013B (en) | 1993-03-01 | 1993-03-01 | Wavelength meter |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2288013B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2330199A (en) * | 1997-10-09 | 1999-04-14 | Zeiss Eltro Optronic Gmbh | Wavelength measuring device for short duration laser pulses |
| GB2353858A (en) * | 1999-09-01 | 2001-03-07 | Bookham Technology Ltd | Optical wavelength measuring device using integrated optics and photodiodes |
-
1993
- 1993-03-01 GB GB9304091A patent/GB2288013B/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2330199A (en) * | 1997-10-09 | 1999-04-14 | Zeiss Eltro Optronic Gmbh | Wavelength measuring device for short duration laser pulses |
| GB2353858A (en) * | 1999-09-01 | 2001-03-07 | Bookham Technology Ltd | Optical wavelength measuring device using integrated optics and photodiodes |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2288013B (en) | 1996-06-19 |
| GB9304091D0 (en) | 1993-04-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20050301 |