# US 7,609,437 B2 · Optical amplifier apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,437 B2 - Document ID: US7609437B2 - Status: Granted - Kind: B2 - Application number: 10/567,646 - Filed: 2004-08-11 - Published: 2007-07-19 - Granted: 2009-10-27 - Earliest claimed: 2003-08-13 - Assignees: Advantest Corporation - Inventors: Atsushi Seki - Web page: https://patentgrep.com/patent/US7609437B2 ## CPC - H04B 10/294: in a multiwavelength system, e.g. gain equalisation - H01S 3/06758: {Tandem amplifiers} - H01S 3/094003: {the pumped medium being a fibre} - H01S 3/005: {Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping (shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B)} - H01S 3/0064: {Anti-reflection devices, e.g. optical isolaters (absorbing layers for marking or protecting purposes in laser working B23K26/50; magneto-optical non-reciprocal devices G02F1/093, G02F1/0955)} - H01S 3/06766: {C-band amplifiers, i.e. amplification in the range of about 1530 nm to 1560 nm} - H01S 3/0677: {L-band amplifiers, i.e. amplification in the range of about 1560 nm to 1610 nm} - 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 An optical amplifier apparatus capable of dealing with different wavelength bands and capable of outputting an amplified light with reduced noise for any one of the wavelength bands. In a case of amplifying a light of C-band, terminals (51,52) of an optical switch (50) are connected to each other. An incident light is amplified by a first front-end optical fiber amplifier (12) and a first back-end optical fiber amplifier (18). The amplified light passes via the terminals (51,52) and through a back-end WDM coupler (36) and goes out of the optical amplifier apparatus (1). In a case of amplifying a light of L-band, terminals (51,54) of the optical switch (50) are connected to each other, while terminals (52,53) thereof are connected to each other. An incident light is amplified by the first front-end optical fiber amplifier (12) and first back-end optical fiber amplifier (18), passing via the terminals (51,54), thereafter being further amplified by a second front-end optical fiber amplifier (22) and a second back-end optical fiber amplifier (28). The thus amplified light then passes via the terminals (53,52) and through the back-end WDM coupler (36) and goes out of the optical amplifier apparatus (1). ## Claims ### Claim 1 An optical amplifier apparatus comprising: a first front-end optical fiber amplifier that amplifies incident light; a first front-end pumping light source that generates first pumping light supplied to said first front-end optical fiber amplifier; a first front-end pumping light introducing section that introduces the first pumping light to said first front-end optical fiber amplifier; a first back-end optical fiber amplifier that amplifies outgoing light of said first front-end optical fiber amplifier; a second front-end optical fiber amplifier; a second front-end pumping light source that generates second pumping light supplied to said second front-end optical fiber amplifier; a second front-end pumping light introducing section that introduces the second pumping light to said second front-end optical fiber amplifier from an outgoing side which is opposite to an incident side; a second back-end optical fiber amplifier that amplifies outgoing light of said second front-end optical fiber amplifier; a back-end pumping light source that generates third pumping light supplied to said first back-end optical fiber amplifier; a back-end pumping light introducing section that introduces the third pumping light to said first back-end optical fiber amplifier; and an optical connecting section that (1) connects an outgoing side of said first back-end optical fiber amplifier and said back-end pumping light introducing section to each other, or (2) connects the outgoing side of said first back-end optical fiber amplifier and the incident side of said second front-end optical fiber amplifier to each other and the outgoing side of said second back-end optical fiber amplifier and said back-end pumping light introducing section to each other, wherein said first front-end pumping light introducing section is disposed between said first front-end optical fiber amplifier and said first back-end optical fiber amplifier; and wherein said second front-end pumping light introducing section is disposed between said second front-end optical fiber amplifier and said second back-end optical fiber amplifier. ### Claim 2 (depends on 1) The optical amplifier apparatus according to claim 1, further comprising: a light blocking section that blocks light from said first back-end optical fiber amplifier from being provided to said first front-end optical fiber amplifier. ### Claim 3 (depends on 1) The optical amplifier apparatus according to claim 1, wherein a gain of said first front-end optical fiber amplifier is set so that a noise of said first back-end optical fiber amplifier can be neglected when said optical connecting section connects the outgoing side of said first back-end optical fiber amplifier and said back-end pumping light introducing section to each other. ### Claim 4 (depends on 3) The optical amplifier apparatus according to claim 3, wherein a combined gain of the gain of said first front-end optical fiber amplifier, a gain of said first back-end optical fiber amplifier, and a gain of said second front-end optical fiber amplifier is set so that a noise of outgoing light of said second back-end optical fiber amplifier is approximately maintained when said optical connecting section connects the outgoing side of said first back-end optical fiber amplifier and the incident side of said second front-end optical fiber amplifier to each other. ### Claim 5 (depends on 1) The optical amplifier apparatus according to claim 1, wherein when said optical connecting section connects the outgoing side of said first back-end optical fiber amplifier and said back-end pumping light introducing section to each, other, a wavelength band of the outgoing light of said first back-end optical fiber amplifier is the C-band. ### Claim 6 (depends on 1) The optical amplifier apparatus according to claim 1, wherein when said optical connecting section connects the outgoing side of said first back-end optical fiber amplifier and the incident side of said second front-end optical fiber amplifier to each other, a wavelength band of the outgoing light of said second back-end optical fiber amplifier is the L-band. ### Claim 7 (depends on 1) The optical amplifier apparatus according to claim 1, wherein at least one of said first front-end optical fiber amplifier, said first back-end optical fiber amplifier, said second front-end optical fiber amplifier, and said second back-end optical fiber amplifier is an Erbium-doped optical fiber. ### Claim 8 (depends on 1) The optical amplifier apparatus according to claim 1, wherein wavelengths of the light generated by said first front-end pumping light source, said second front-end pumping light source, and said back-end pumping light source are 980 nm. ### Claim 9 (depends on 1) The optical amplifier apparatus according to claim 1, comprising: a third front-end optical fiber amplifier that amplifies the outgoing light of said second front-end optical fiber amplifier, and emits amplified light to said second back-end optical fiber amplifier; a third front-end pumping light source that generates fourth pumping light supplied to said third front-end optical fiber amplifier; and a third front-end pumping light introducing means that introduces the fourth pumping light to said third front-end optical fiber amplifier from an outgoing side which is opposite to an incident side. ### Claim 10 An optical amplifier apparatus comprising: a first front-end optical fiber amplifier that amplifies incident light; a first front-end pumping light source that generates first pumping light supplied to said first front-end optical fiber amplifier; a first front-end pumping light coupler that introduces the first pumping light to said first front-end optical fiber amplifier; a first back-end optical fiber amplifier that amplifies outgoing light of said first front-end optical fiber amplifier; a second front-end optical fiber amplifier; a second front-end pumping light source that generates second pumping light supplied to said second front-end optical fiber amplifier; a second front-end pumping light coupler that introduces the second pumping light to said second front-end optical fiber amplifier from an outgoing side which is opposite to an incident side; a second back-end optical fiber amplifier that amplifies outgoing light of said second front-end optical fiber amplifier; a back-end pumping light source that generates third pumping light supplied to said first back-end optical fiber amplifier; a back-end pumping light coupler that introduces the third pumping light to said first back-end optical fiber amplifier; and an optical switch that (1) connects an outgoing side of said first back-end optical fiber amplifier and said back-end pumping light coupler to each other, or (2) connects the outgoing side of said first back-end optical fiber amplifier and the incident side of said second front-end optical fiber amplifier to each other and the outgoing side of said second back-end optical fiber amplifier and said back-end pumping light coupler to each other, wherein said first front-end pumping light coupler is disposed between said first front-end optical fiber amplifier and said first back-end optical fiber amplifier; and wherein said second front-end pumping light coupler is disposed between said second front-end optical fiber amplifier and said second back-end optical fiber amplifier. ### Claim 11 (depends on 10) The optical amplifier apparatus according to claim 10, comprising an optical isolator that blocks light from said first back-end optical fiber amplifier from being provided to said first front-end optical fiber amplifier. ### Claim 12 (depends on 10) The optical amplifier apparatus according to claim 10, wherein a gain of said first front-end optical fiber amplifier is set so that a noise of said first back-end optical fiber amplifier can be neglected when said optical switch connects the outgoing side of said first back-end optical fiber amplifier and said back-end pumping light coupler to each other. ### Claim 13 (depends on 12) The optical amplifier apparatus according to claim 12, wherein a combined gain of the gain of said first front-end optical fiber amplifier, a gain of said first back-end optical fiber amplifier, and a gain of said second front-end optical fiber amplifier is set so that a noise of outgoing light of said second back-end optical fiber amplifier is approximately maintained when said optical switch connects the outgoing side of said first back-end optical fiber amplifier and the incident side of said second front-end optical fiber amplifier to each other. ### Claim 14 (depends on 10) The optical amplifier apparatus according to claim 10, wherein a wavelength band of the outgoing light of said first back-end optical fiber amplifier is the C-band when said optical switch connects the outgoing side of said first back-end optical fiber amplifier and said back-end pumping light coupler to each other. ### Claim 15 (depends on 10) The optical amplifier apparatus according to claim 10, wherein a wavelength band of the outgoing light of said second back-end optical fiber amplifier is the L-band when said optical switch connects the outgoing side of said first back-end optical fiber amplifier and the incident side of said second front-end optical fiber amplifier to each other. ### Claim 16 (depends on 10) The optical amplifier apparatus according to claim 10, wherein at least one of said first front-end optical fiber amplifier, said first back-end optical fiber amplifier, said second front-end optical fiber amplifier, and said second back-end optical fiber amplifier is an Erbium-doped optical fiber. ### Claim 17 (depends on 10) The optical amplifier apparatus according to claim 10, wherein wavelengths of the light generated by said first front-end pumping light source, said second front-end pumping light source, and said back-end pumping light source are 980 nm. ### Claim 18 (depends on 10) The optical amplifier apparatus according to claim 10, further comprising: a third front-end optical fiber amplifier that amplifies the outgoing light of said second front-end optical fiber amplifier, and emits amplified light to said second back-end optical fiber amplifier; a third front-end pumping light source that generates fourth pumping light supplied to said third front-end optical fiber amplifier; and a third front-end pumping light coupler that introduces the fourth pumping light to said third front-end optical fiber amplifier from an outgoing side which is opposite to an incident side.