Optical clock signal extraction using non-linear optical modulator

• US 5,828,679 A
• Filed: 07/23/1997
• Issued: 10/27/1998
• Est. Priority Date: 09/08/1992
• Status: Expired due to Term

• Current Assignee: British Telecommunications PLC (BT Group PLC)
• Original Assignee: British Telecommunications PLC (BT Group PLC)
• Inventors: Fisher, Michael Andreja
• Primary Examiner(s): Lee, John D.
• Application Number:
  US08/899,124
• Time in Patent Office: 461 Days
• Field of Search: 372/6, 372/18, 372/25, 372/26, 372/28, 372/29, 372/30, 372/32, 372/33, 372/38, 359/158, 359/326-332, 359/340, 359/341, 359/346
• US Class Current: 372/6
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02F 1/017 Structures with periodic or quasi periodic potential variation, e.g. superlattices, quantum wells
• CPC Class Codes: G02F 1/01716 Optically controlled superlattice or quantum well devices
• CPC Class Codes: G02F 1/2257 the optical waveguides being made of semiconducting material
• CPC Class Codes: G02F 1/3133 the optical waveguides being made of semiconducting materials
• CPC Class Codes: G02F 1/3515 All-optical modulation, gating, switching, e.g. control of a light beam by another light beam G02F1/353, G02F1/37, G02F1/39 take precedence
• CPC Class Codes: G02F 1/3556 Semiconductor materials, e.g. quantum wells
• CPC Class Codes: G02F 2/004 Transferring the modulation of modulated light, i.e. transferring the information from one optical carrier of a first wavelength to a second optical carrier of a second wavelength, e.g. all-optical wavelength converter
• CPC Class Codes: G02F 2202/108 quantum wells
• CPC Class Codes: G02F 3/00 Optical logic elements; Optical bistable devices
• CPC Class Codes: G02F 3/02 Optical bistable devices

Abstract

A non-linear semiconductor optical device includes an active waveguide with a multiple quantum well construction in the active region. The device is supplied with a drive current at the material transparency current with respect to an optical pump. An optical non-linearity appears with respect to input radiation having a wavelength below that of the bandgap equivalent wavelength of the active region (λ<λg), the effect being achieved at relatively low optical input powers. The non-linearity is fast enough that a switching device incorporating the invention, in use as a demultiplexer, has potential to be used at bit rates approaching the Tbit/s range. In a demultiplexer embodiment, the non-linearity may be exploited in a directional coupler, an optical pump being used intermittently to control cross-over of an incoming TDM data signal so as to "pick off" a selected channel. Other applications include optical logic devices.

Claims

1. A method of extracting a clock signal from an optical data stream, the method comprising:

mode locking an optical fibre laser with the data stream to produce a stream of laser pulses at the clock frequency,

the optical fibre laser including a resonant cavity within which is locked a non-linear optical modulator including a semiconductor optical amplifier which is biased at transparency.

2. A method as in claim 1 wherein the data stream is an optical time division multiplexed data signal.

3. A method as in claim 2 wherein the data stream has a data rate of at least 100 Gbit/s.

4. A clock extraction device for extracting a clock signal from an optical data stream, the device comprising:

an optical fibre laser having a resonant cavity which incorporates a non-linear optical modulator,

input means to permit, in use, the optical data stream to be coupled into the resonant cavity for passage through the optical modulator;

the arrangements being such that the laser can, in use, be mode-locked by the data stream, and

output means to permit pulses produced by the mode-locked laser to be coupled out from the cavity;

wherein the non-linear optical modulator is a semiconductor optical amplifier which is, in use, biased at transparency.

5. A device as in claim 4 which is configured to extract a clock signal of at least 10 GHz.

6. A device as in claim 5, wherein the semiconductor optical amplifier has an active layer comprising a multiple quantum well material.

7. A device as in claim 6, wherein the optical amplifier is configured for operation with optical wavelengths in the region of 1.5 to 1.55 μ

m.

8. An all-optical clock recovery device comprising:

an optical laser incorporating a semi-conductor optical amplifier biased at transparency within an optically resonant cavity;

an optical input port to mode lock said optically resonant cavity with an optical data stream input therethrough; and

an optical output port to output optical mode-locked output pulses from said optical cavity.

9. An all-optical clock recovery method comprising:

using an input optical data stream to mode lock an optical laser incorporating a semi-conductor optical amplifier biased at transparency with an optically resonant cavity; and

outputting mode-locked optical pulses from said cavity.

10. A method of extracting a clock signal from an optical data stream, the method comprising:

mode locking an optical fibre laser with the data stream to produce a stream of laser pulses at the clock frequency,

the optical fibre laser including a resonant cavity within which is located a non-linear optical modulator including a semiconductor optical amplifier which is biased at transparency for the radiation of the optical data stream having a wavelength shorter than a bandgap equivalent wavelength of an active amplifier region.

11. A method as in claim 10 wherein the data stream is an optical time division multiplexed data signal.

12. A method as in claim 11 wherein the data stream has a data rate of at least 100 Gbit/s.

13. A clock extraction device for extracting a clock signal from an optical data stream, the device comprising:

an optical fibre laser having a resonant cavity which incorporates a non-linear optical modulator,

input means to permit, in use, the optical data stream to be coupled into the resonant cavity for passage through the optical modulator;

the arrangements being such that the laser can, in use, be mode-locked by the data stream, and

output means to permit pulses produced by the mode-locked laser to be coupled out from the cavity;

wherein the non-linear optical modulator is a semiconductor optical amplifier which is, in use, biased at transparency for the radiation of the optical data stream having a wavelength shorter than a bandgap equivalent wavelength of an active amplifier region.

14. A device as in claim 13 which is configured to extract a clock signal of at least 10 GHz.

15. A device as in claim 14, wherein the semiconductor optical amplifier has an active layer comprising a multiple quantum well material.

16. A device as in claim 15, wherein the optical amplifier is configured for operation with optical wavelengths in the region of 1.5 to 1.55 μ

m.

17. An all-optical clock recovery device comprising:

an optical laser incorporating a semi-conductor optical amplifier biased at transparency within an optically resonant cavity;

an optical input port to mode lock said optically resonant cavity with an optical data stream input therethrough; and

an optical output port to output optical mode-locked output pulses from said optical cavity

wherein the radiation of the optical data stream has a wavelength shorter than a bandgap equivalent wavelength of an active amplifier region.

18. An all-optical clock recovery method comprising:

using an input optical data stream to mode lock an optical laser incorporating a semi-conductor optical amplifier biased at transparency within an optically resonant cavity; and

outputting mode-locked optical pulses from said cavity;

wherein the radiation of the optical data stream has a wavelength shorter than a bandgap equivalent wavelength of an active amplifier region.