Optical transmission apparatus

• US 20040190123A1
• Filed: 03/05/2004
• Published: 09/30/2004
• Est. Priority Date: 03/26/2003
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Murakami, Makoto, Noheji, Kiyotoshi, Nakamura, Eisuke
• Granted Patent: US 7,139,117 B2
• Time in Patent Office: Days
• US Class Current: 359/337
• CPC Class Codes: H04B 10/2916 using Raman or Brillouin amplifiers
• CPC Class Codes: H04B 10/2942 using automatic gain control [AGC] H04B10/296 takes precedence

Abstract

An optical transmission apparatus that improves optical transmission quality by performing an optical noise correction and optical level detection with great precision. A first optical amplifier performs optical amplification with an optical fiber transmission line as an amplification medium. A second optical amplifier inputs second excitation light into an amplification medium in which an active substance for optical amplification is doped to perform optical amplification. A first optical level detector monitors, before transmitting an optical signal, a level of optical noise scattered by the first optical amplifier by emitting first excitation light in an operating environment and detects an optical level at the time of transmitting the optical signal by subtracting the level of the optical noise from a signal amplified by the first optical amplifier. A second optical level detector monitors, before transmitting an optical signal, a level of optical noise emitted from the second optical amplifier by emitting the second excitation light in the operating environment and detects an optical level at the time of transmitting the optical signal by subtracting the level of the optical noise from a signal amplified by the second optical amplifier.

Claims

1. An optical transmission apparatus for amplifying and transmitting an optical signal, the apparatus comprising:

a first optical amplifier for inputting first excitation light into an optical fiber transmission line to perform optical amplification with the optical fiber transmission line as an amplification medium;

a second optical amplifier for inputting second excitation light into an amplification medium in which an active substance for optical amplification is doped to perform optical amplification;

a first optical level detector for monitoring, before transmitting an optical signal, a level of optical noise scattered by the first optical amplifier by emitting the first excitation light and for detecting an optical level at the time of transmitting the optical signal by subtracting the level of the optical noise monitored from a signal amplified by the first optical amplifier; and

a second optical level detector for monitoring, before transmitting an optical signal, a level of optical noise emitted from the second optical amplifier by emitting the second excitation light and for detecting an optical level at the time of transmitting the optical signal by subtracting the level of the optical noise monitored from a signal amplified by the second optical amplifier.

2. The optical transmission apparatus according to claim 1, wherein:

the first optical level detector and the second optical level detector maintain or vary excitation light power according to operating conditions; and

if the first optical level detector and the second optical level detector vary excitation light power, the first optical level detector and the second optical level detector monitor a plurality of optical noise levels corresponding to a plurality of excitation light power values and, at the time of transmitting an optical signal, perform correction with an optical noise level corresponding to a excitation light power value used.

3. An optical transmission apparatus for amplifying and transmitting an optical signal, the apparatus comprising:

a first optical amplifier for inputting a plurality of first excitation light beams with different wavelengths into an optical fiber transmission line to perform optical amplification with the optical fiber transmission line as an amplification medium;

a second optical amplifier for inputting a plurality of second excitation light beams with different wavelengths into an amplification medium in which an active substance for optical amplification is doped to perform optical amplification;

a first optical level detector for monitoring, before transmitting an optical signal, a profile of optical noise scattered by the first optical amplifier by emitting the first excitation light beams, and recognizing a difference in optical noise level according to wavelengths from monitoring results and for controlling, at the time of transmitting the optical signal, excitation light power so as to prevent the difference according to wavelengths from arising, and detecting an optical level by subtracting an optical noise level monitored from a signal amplified by the first optical amplifier; and

a second optical level detector for monitoring, before transmitting an optical signal, a profile of optical noise emitted from the second optical amplifier by emitting the second excitation light beams, and recognizing a difference in optical noise level according to wavelengths from monitoring results and for controlling, at the time of transmitting the optical signal, excitation light power so as to prevent the difference according to wavelengths from arising, and detecting an optical level by subtracting an optical noise level monitored from a signal amplified by the second optical amplifier.

4. An optical transmission apparatus for amplifying and transmitting an optical signal, the apparatus comprising:

an optical amplifier for inputting excitation light into an optical fiber transmission line to perform optical amplification with the optical fiber transmission line as an amplification medium; and

an optical level detector for monitoring, before transmitting an optical signal, a level of optical noise scattered by the optical amplifier by emitting the excitation light and for detecting an optical level at the time of transmitting the optical signal by subtracting the level of the optical noise monitored from a signal amplified by the optical amplifier.

5. The optical transmission apparatus according to claim 4, wherein:

the optical level detector maintains or varies excitation light power according to operating conditions; and

if the optical level detector varies excitation light power, the optical level detector monitors a plurality of optical noise levels corresponding to a plurality of excitation light power values and, at the time of transmitting an optical signal, performs correction with an optical noise level corresponding to a excitation light power value used.

6. An optical transmission apparatus for amplifying and transmitting an optical signal, the apparatus comprising:

an optical amplifier for inputting excitation light into an amplification medium in which an active substance for optical amplification is doped to perform optical amplification; and

an optical level detector for monitoring, before transmitting an optical signal, a level of optical noise emitted from the optical amplifier by emitting the excitation light and for detecting an optical level at the time of transmitting the optical signal by subtracting the level of the optical noise monitored from a signal amplified by the optical amplifier.

7. The optical transmission apparatus according to claim 6, wherein:

the optical level detector maintains or varies excitation light power according to operating conditions; and

if the optical level detector varies excitation light power, the optical level detector monitors a plurality of optical noise levels corresponding to a plurality of excitation light power values and, at the time of transmitting an optical signal, performs correction with an optical noise level corresponding to a excitation light power value used.

8. An optical transmission apparatus for amplifying and transmitting an optical signal, the apparatus comprising:

an optical amplifier for inputting a plurality of excitation light beams with different wavelengths into an amplification medium in which an active substance for optical amplification is doped to perform optical amplification; and

an optical level detector for monitoring, before transmitting an optical signal, a profile of optical noise emitted from the optical amplifier by emitting the excitation light beams, and recognizing a difference in optical noise level according to wavelengths from monitoring results and for controlling, at the time of transmitting the optical signal, excitation light power so as to prevent the difference according to wavelengths from arising, and detecting an optical level by subtracting an optical noise level monitored from a signal amplified by the optical amplifier.

9. An optical transmission apparatus for amplifying and transmitting an optical signal, the apparatus comprising:

an optical amplifier for inputting a plurality of excitation light beams with different wavelengths into an optical fiber transmission line to perform optical amplification with the optical fiber transmission line as an amplification medium; and

an optical level detector for monitoring, before transmitting an optical signal, a profile of optical noise scattered by the optical amplifier by emitting the excitation light beams, and recognizing a difference in optical noise level according to wavelengths from monitoring results and for controlling, at the time of transmitting the optical signal, excitation light power so as to prevent the difference according to wavelengths from arising, and detecting an optical level by subtracting an optical noise level monitored from a signal amplified by the optical amplifier.

10. An optical transmission apparatus for amplifying and transmitting an optical signal, the apparatus comprising:

an optical amplifier for amplifying an optical signal;

a reference light emission section for emitting reference light by which a reference level value will be obtained at an output power determination point behind the optical amplifier; and

an optical level detector for measuring power at the output power determination point, and finding out a differential value between the reference level value and a measured value and for measuring, at the time of transmitting an optical signal, a level of a main signal included in the optical signal amplified by the optical amplifier according to transmission wavelengths, and detecting an optical level by correcting a measurement result with the differential value.

11. An optical transmission apparatus for amplifying and transmitting an optical signal, the apparatus comprising:

a reference light emission section for emitting reference light by which a reference level value will be obtained at an input power determination point; and

an optical level detector for measuring power at the input power determination point, and finding out a differential value between the reference level value and a measured value and for measuring, at the time of transmitting an optical signal, a level of a main signal included in the input optical signal according to transmission wavelengths, and detecting an optical level by correcting a measurement result with the differential value.

12. An optical transmission apparatus for amplifying and transmitting an optical signal, the apparatus comprising:

an optical amplifier for amplifying an optical signal;

an input-side reference light emission section for emitting reference light by which an input reference level value will be obtained at an input power determination point;

an output-side reference light emission section for emitting reference light by which an output reference level value will be obtained at an output power determination point behind the optical amplifier; and

an optical level detector for measuring power at the input power determination point, finding out a differential value between the input reference level value and a measured value, measuring, at the time of transmitting an optical signal, a level of a main signal included in the input optical signal according to transmission wavelengths, and detecting an optical level of the input optical signal by correcting a measurement result with the differential value, and for measuring power at the output power determination point, finding out a differential value between the output reference level value and a measured value, measuring, at the time of transmitting an optical signal, a level of a main signal included in the optical signal amplified by the optical amplifier according to transmission wavelengths, and detecting an optical level of the amplified signal by correcting a measurement result with the differential value.

13. An optical transmission apparatus for amplifying and transmitting an optical signal, the apparatus comprising:

an optical amplifier for amplifying an optical signal;

a reference light emission section for emitting reference light to set an input reference level value at an input power determination point before the optical amplifier or an output reference level value at an output power determination point behind the optical amplifier by switching; and

an optical level detector for measuring power at the input power determination point, finding out a differential value between the input reference level value and a measured value, measuring, at the time of transmitting an optical signal, a level of a main signal included in the input optical signal according to transmission wavelengths, and detecting an optical level of the input optical signal by correcting a measurement result with the differential value to set the input reference level value, and for measuring power at the output power determination point before transmitting an optical signal, finding out a differential value between the output reference level value and a measured value, measuring, at the time of transmitting the optical signal, a level of a main signal included in the optical signal amplified by the optical amplifier according to transmission wavelengths, and detecting an optical level of the amplified signal by correcting a measurement result with the differential value to set the output reference level value.