# US 9,520,694 B2 · Optical amplifier with loss adjustment unit based on gain

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- Number: US 9,520,694 B2
- Document ID: US9520694B2
- Status: Granted
- Kind: B2
- Application number: 14/631,165
- Filed: 2015-02-25
- Published: 2015-10-01
- Granted: 2016-12-13
- Earliest claimed: 2014-03-28
- Assignees: Fujitsu Limited
- Applicants: Fujitsu Limited
- Inventors: Yoshito Kachita; Tomoaki Takeyama; Norifumi Shukunami
- Web page: https://patentgrep.com/patent/US9520694B2

## CPC

- H01S 3/06758: {Tandem amplifiers}
- H01S 3/10015: {by monitoring or controlling, e.g. attenuating, the input signal}
- H01S 3/13013: {by controlling the optical pumping}
- H04B 10/00: Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B 10/2942: {using automatic gain control [AGC] (H04B10/296 takes precedence)}
- H01S 3/10069: {Memorized or pre-programmed characteristics, e.g. look-up table [LUT]}
- H01S 3/1608: {erbium}
- H01S 2301/02: ASE (amplified spontaneous emission), noise; Reduction thereof
- H01S 2301/04: Gain spectral shaping, flattening
- H04B 2210/003: Devices including multiple stages, e.g., multi-stage optical amplifiers or dispersion compensators
- 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
- H04B: TRANSMISSION

## Abstract

An optical amplifier includes an optical amplifying unit, a splitting unit, and a loss adjusting unit. The optical amplifying unit provides gain to wavelength multiplexed light received from a transmission line, to amplify light intensity. The splitting unit splits the amplified wavelength multiplexed light. The loss adjusting unit adjusts loss provided to each wavelength of a first portion of the split wavelength multiplexed light based on the gain.

## Claims

### Claim 1

An optical amplifier comprising:
an optical amplifying unit that provides a gain to wavelength multiplexed light received from a transmission line, to amplify light intensity, the wavelength multiplexed light including signals at respective wavelengths, the gain being determined according to a loss caused on the transmission line;
a splitting unit that splits the amplified wavelength multiplexed light into a first portion at a predetermined wavelength and a second portion at a wavelength other than the predetermined wavelength;
an attenuation amount output unit that outputs attenuation amounts respectively provided to signals of the first portion of the split wavelength multiplexed light, the attenuation amounts being determined according to a value of the gain; and
a calculating unit that calculates a gain provided to the optical amplifying unit based on the value of the gain, a light intensity at all wavelengths of the wavelength multiplexed light received from the transmission line, and a light intensity of a signal included in the second portion, wherein
the splitting unit attenuates each of the signals of the first portion respectively according to the attenuation amounts output by the attenuation amount output unit.

### Claim 2

An optical amplifier comprising:
an optical amplifying unit that provides a gain to wavelength multiplexed light received from a transmission line, to amplify light intensity, the wavelength multiplexed light including signals at respective wavelengths, the gain being determined according to a loss caused on the transmission line;
an adding unit that adds a signal of light at a predetermined wavelength to the amplified wavelength multiplexed light;
a calculating unit that calculates a gain provided to the optical amplifying unit based on a value of the gain, a light intensity at all wavelengths of the wavelength multiplexed light received from the transmission line, and a light intensity of the added signal of the light at the predetermined wavelength; and
an attenuation amount output unit that outputs attenuation amounts respectively provided to signals of the wavelength multiplexed light including the signal of the light at the predetermined wavelength, the attenuation amounts being determined according to the value of the gain, wherein
the adding unit attenuates the signals of the wavelength multiplexed light respectively according to the attenuation amounts output by the attenuation amount output unit.

### Claim 3

An optical amplifier comprising:
an optical amplifying unit that provides a gain to wavelength multiplexed light received from a transmission line, to amplify light intensity, the wavelength multiplexed light including signals at respective wavelengths, the gain being determined according to a loss caused on the transmission line;
a splitting unit that splits the amplified wavelength multiplexed light into a first portion at a predetermined wavelength and a second portion at a wavelength other than the predetermined wavelength;
an attenuation amount output unit that outputs attenuation amounts respectively provided to signals of the first portion of the split wavelength multiplexed light, the attenuation amounts being determined according to a value of the gain;
an adding unit that adds a signal of light at a predetermined wavelength to the amplified wavelength multiplexed light; and
a calculating unit that calculates a gain provided to the optical amplifying unit based on the value of the gain, a light intensity at all wavelengths of the wavelength multiplexed light received from the transmission line, a light intensity of a signal included in the second portion, and a light intensity of the added signal of the light at the predetermined wavelength, wherein
the adding unit attenuates the signals of the first portion respectively according to the attenuation amounts output by the attenuation amount output unit.

### Claim 4 (depends on 1)

The optical amplifier according to claim 1, wherein the attenuation amount output unit outputs the attenuation amounts indicated on a table that associates attenuation amounts respectively provided to the signals of the first portion with the gain determined according to a loss caused in the transmission line.