Laser light sources

Claim 2

An injection-locked pair of optical lasers which together provide a coherent light source comprising: gas laser means for generating a narrow linewidth first coherent light output, semiconductor laser means biased for generating a less-narrow linewidth second coherent light output serving as the coherent output of said light source; and injection-locking means for injecting at least a portion of the narrow linewidth first coherent light output into the semiconductor laser means so as to injection-lock the semiconductor laser means into a predetermined mode of lasing operation which stabilizes said second coherent light output at a predetermined wavelength and linewidth.

Claim 3

A light source according to claim 1 wherein said gas laser means comprises a helium-neon gas laser.

Claim 4

A light source according to claim 1 in which the semiconductor laser means comprises a buried crescent semiconductor laser.

Claim 5

A light source according to claim 1 wherein the semiconductor laser means comprises a plurality of semiconductor lasers.

Claim 6

A light source according to claim 4 further comprising means to frequency offset at least one of said plurality of semiconductor lasers.

Claim 7

A light source according to claim 1 wherein the gas laser means operates at a wavelength in the region of 1.5 μm.

Claim 8

A transmitter for use in a coherent optical fibre communication system, said transmitter comprising: gas laser means generating a narrow linewidth first coherent light output, semiconductor laser means arranged and biased for generating a less-narrow linewidth second coherent light output serving as the coherent optical output of said transmitter; injection-locking means for injecting at least a portion of the narrow linewidth first coherent light output into the semiconductor laser means so as to injection-lock the semiconductor laser into a predetermined mode of lasing operation which stabilizes said second coherent light output at a predetermined wavelength and linewidth; and modulating means for modulating the second coherent light output with a supplied modulation input signal and thereby to generate a modulated light output.

Claim 9

A transmitter for use in a coherent optical fibre communication system, said transmitter comprising: gas laser means generating a narrow linewidth first coherent light output, semiconductor laser means arranged and biased for generating a less-narrow linewidth second coherent light output serving as the coherent optical output of said transmitter; injection-locking means for injecting at least a portion of the narrow linewidth first coherent light output into the semiconductor laser means so as to injection-lock the semiconductor laser into a predetermined mode of lasing operation which stabilizes said second coherent light output at a predetermined wavelength and linewidth; and modulating means for modulating the second coherent light output with a supplied modulation input signal and thereby to generate a modulated light output.

Claim 10

A transmitter according to claim 7 wherein said modulating means comprises means to frequency shift key the second coherent light output.

Claim 11

A transmitter according to claim 7 wherein said modulating means comprises means to phase shift key the second coherent light output.

Claim 12

A transmitter for a coherent optical communication system, which transmitter comprises: a gas laser light source to generate narrow linewidth laser light, a semiconductor laser light source including at least one semiconductor laser to generate laser light at a semiconductor laser output linewidth, means to inject at least a portion of said narrow linewidth laser light into said semiconductor laser light source, thereby to reduce the semiconductor laser output linewidth, and modulating means to produce a modulated light output from said semiconductor laser light source.

Claim 13

A transmitter for a coherent optical communication system, which transmitter comprises: a gas laser light source to generate narrow linewidth laser light, a semiconductor laser light source including at least one semiconductor laser to generate laser light at a semiconductor laser output linewidth, means to inject at least a portion of said narrow linewidth laser light into said semiconductor laser light source, thereby to reduce the semiconductor laser output linewidth, and modulating means to produce a modulated light output from said semiconductor laser light source.

Claim 14

A transmitter according to claim 10 wherein said gas laser comprises a Helium-Neon gas laser.

Claim 15

A transmitter according to claim 10 wherein said semiconductor laser comprises a buried crescent semiconductor laser.

Claim 16

A transmitter according to claim 10 wherein said semiconductor laser comprises a plurality of semiconductor lasers.

Claim 17

A transmitter according to claim 13, further comprising means to frequency offset at least one of said plurality of semiconductor lasers.

Claim 18

A transmitter according to claims 10, 11, 12, 13 or 14 wherein the gas laser operates at a wavelength in the region of 1.5 μm.

Claim 19

A transmitter according to claim 10 wherein the modulating means include phase shift keying means for phase shift keying the light output from said semiconductor laser.

Claim 20

A transmitter according to claim 10 wherein the modulating means comprise frequency shift keying means for frequency shift keying the light output from said semiconductor laser.

Claim 21

A coherent optical oscillator for use in a coherent optical communication system, said oscillator comprising: a first optical oscillator including a gas laser producing a first optical oscillator output; a second optical oscillator including a semiconductor laser producing a second optical oscillator output; and injection means for injecting at least a part of said first optical output into said second optical oscillator so as to optically couple and injection-lock the operation of the second optical oscillator thereto.

Claim 22

A coherent optical oscillator for use in a coherent optical communication system, said oscillator comprising: a first optical oscillator including a gas laser producing a first optical oscillator output; a second optical oscillator including a semiconductor laser producing a second optical oscillator output; and injection means for injecting at least a part of said first optical output into said second optical oscillator so as to optically couple and injection-lock the operation of the second optical oscillator thereto.