# US 7,609,977 B2 · Optical transmission using semiconductor optical amplifier (SOA) > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,977 B2 - Document ID: US7609977B2 - Status: Granted - Kind: B2 - Application number: 11/894,509 - Filed: 2007-08-20 - Published: 2008-07-03 - Granted: 2009-10-27 - Earliest claimed: 2002-12-03 - Assignees: Finisar Corporation - Inventors: Yasuhiro Matsui; Daniel Mahgerefteh; Xueyan Zheng; Kevin McCallion; Parviz Tayebati - Web page: https://patentgrep.com/patent/US7609977B2 ## CPC - G02B 5/281: {designed for the infrared light} - H04B 10/25133: {including a lumped electrical or optical dispersion compensator (H04B10/2519, H04B10/2525 takes precedence)} - H04B 10/504: {using direct modulation} - H01S 5/50: Amplifier structures not provided for in groups H01S5/02 - H01S5/30 - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - H04B: TRANSMISSION - 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 ## Abstract A fiber optic communication system is disclosed having an optical signal source adapted to produce an amplitude and frequency modulated signal encoding binary data wherein high intensity 1 bits are red shifted relative to lower intensity 0 bits. The amplitude and frequency modulated signal is transmitted through a semiconductor optical amplifier (SOA), which may operate in saturation. An optical spectrum reshaper (OSR) is adapted to reshape the output of the SOA. ## Claims ### Claim 1 A fiber optic communication system comprising: an optical signal source adapted to receive a binary first signal and generate a binary second signal, wherein the binary first signal has an amplitude modulated component, wherein the binary second signal has an amplitude modulated component and a frequency modulated component, and further wherein the binary second signal is characterized in that the higher intensity 1 bits are red shifted relative to the lower intensity 0 bits; a semiconductor optical amplifier (SOA) adapted to receive the binary second signal and generate a binary third signal, wherein the binary third signal has an amplitude modulated component and a frequency modulated component, and further wherein the semiconductor optical amplifier operates in saturation; and an optical spectrum reshaper (OSR) adapted to reshape the binary third signal into a binary fourth signal, wherein the binary fourth signal has an amplitude modulated component and a frequency modulated component. ### Claim 2 (depends on 1) A fiber optic communication system according to claim 1 wherein the optical signal source comprises a laser, and further wherein the binary second signal is generated through intra-cavity loss modulation of the laser. ### Claim 3 (depends on 2) A fiber optic communication system according to claim 2 wherein the laser comprises a cavity including a semiconductor material, and further wherein the intra-cavity loss modulation is achieved by applying an appropriate voltage to the semiconductor material so as to effect a change in the absorption of the semiconductor material. ### Claim 4 (depends on 3) A fiber optic communication system according to claim 3 wherein the intra-cavity loss modulation is achieved by using one from the group consisting of: (i) the quantum confined stark effect (QCSE); and (ii) the Franz-Keldysh effect. ### Claim 5 (depends on 2) A fiber optic communication system according to claim 2 wherein the laser comprises one from the group consisting of: (i) distributed feedback (DFB) lasers; (ii) distributed Bragg reflector (DBR) lasers; (iii) sampled grating distributed Bragg reflector (SG-DBR) lasers; and (iv) Y branch DBR lasers. ### Claim 6 (depends on 2) A fiber optic communication system according to claim 2 wherein the laser comprises one from the group consisting of: (i) external cavity lasers with fiber Bragg gratings; (ii) external cavity lasers with ring resonators; (iii) external cavity lasers with planar lightwave circuit (PLC) Bragg gratings; (iv) external cavity lasers with arrayed waveguide gratings (AWG); (v) external cavity lasers with grating filters; (vi) vertical cavity surface emitting lasers (VCSEL); and (vii) Fabry Perot lasers. ### Claim 7 (depends on 1) A fiber optic communication system according to claim 1 wherein the optical spectrum reshaper (OSR) comprises a filter. ### Claim 8 (depends on 7) A fiber optic communication system according to claim 7 wherein the filter has a high frequency side and a low frequency side, and further wherein the system is configured to use the high frequency side of the filter so as to compensate for negative dispersion in a downstream fiber transmission link. ### Claim 9 (depends on 1) A fiber optic communication system according to claim 1 wherein the optical signal source comprises a plurality of lasers, and further wherein the output of each of the lasers is directed into the input of the semiconductor optical amplifier (SOA). ### Claim 10 (depends on 9) A fiber optic communication system according to claim 9 wherein the plurality of lasers together cover a range of wavelengths. ### Claim 11 A method for transmitting a signal, comprising: receiving a binary first signal having an amplitude modulated component and generating a binary second signal having an amplitude modulated component and a frequency modulated component, wherein the binary second signal is characterized in that the higher intensity 1 bits are red shifted relative to the lower intensity 0 bits; passing the binary second signal through a semiconductor optical amplifier (SOA) operating in saturation so as to generate a binary third signal, wherein the binary third signal has an amplitude modulated component and a frequency modulated component; and reshaping the binary third signal into a binary fourth signal, wherein the binary fourth signal has an amplitude modulated component and a frequency modulated component. ### Claim 12 (depends on 11) A method according to claim 11 wherein the binary second signal is generated by a laser utilizing intra-cavity loss modulation. ### Claim 13 (depends on 12) A method according to claim 12 wherein the laser comprises a cavity including a semiconductor material, and further wherein the intra-cavity loss modulation is achieved by applying an appropriate voltage to the semiconductor material so as to effect a change in the absorption of the semiconductor material. ### Claim 14 (depends on 13) A method according to claim 13 wherein the intra-cavity loss modulation is achieved by using one from the group consisting of: (i) the quantum confined stark effect (QCSE); and (ii) the Franz-Keldysh effect. ### Claim 15 (depends on 12) A method according to claim 12 wherein the laser comprises one from the group consisting of: (i) distributed feedback (DFB) lasers; (ii) distributed Bragg reflector (DBR) lasers; (iii) sampled grating distributed Bragg reflector (SG-DBR) lasers; and (iv) Y branch DBR lasers. ### Claim 16 (depends on 12) A method according to claim 12 wherein the laser comprises one from the group consisting of: (i) external cavity lasers with fiber Bragg gratings; (ii) external cavity lasers with ring resonators; (iii) external cavity lasers with planar lightwave circuit (PLC) Bragg gratings; (iv) external cavity lasers with arrayed waveguide gratings (AWG); (v) external cavity lasers with grating filters; (vi) vertical cavity surface emitting lasers (VCSEL); and (vii) Fabry Perot lasers. ### Claim 17 (depends on 11) A method according to claim 11 wherein reshaping the binary third signal into a binary fourth signal is achieved by passing the binary third signal through a filter. ### Claim 18 (depends on 17) A method according to claim 17 wherein the filter has a high frequency side and a low frequency side, and further wherein the high frequency side of the filter is used so as to compensate for negative dispersion in a downstream fiber transmission link. ### Claim 19 (depends on 11) A method according to claim 11 wherein the optical signal source comprises a plurality of lasers, and further wherein the output of each of the lasers is directed into the input of the semiconductor optical amplifier (SOA). ### Claim 20 (depends on 19) A method according to claim 19 wherein generating the binary second signal comprises (i) providing a plurality of optical signal sources covering a range of wavelengths, (ii) selecting one of the plurality of optical signal sources based upon the wavelength desired for the binary second signal, and (iii) directing the binary first signal into the selected optical signal source so as to generate the desired binary second signal.