Optical amplifier

• US 6,532,102 B2
• Filed: 06/26/2001
• Issued: 03/11/2003
• Est. Priority Date: 02/22/2001
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kobayashi, Hideki, Takahashi, Tsukasa, Ohtani, Toshihiro, Izumi, Futoshi, Mori, Shota
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US09/891,205
• Publication Number:
  US 20020114060A1
• Time in Patent Office: 623 Days
• Field of Search: 359/334, 359/341.44
• US Class Current: 359/334
• CPC Class Codes: H04B 10/03 Arrangements for fault recovery
• CPC Class Codes: H04B 10/0775 Performance monitoring and measurement of transmission parameters
• CPC Class Codes: H04B 10/0777 Monitoring line amplifier or line repeater equipment
• CPC Class Codes: H04B 10/2916 using Raman or Brillouin amplifiers
• CPC Class Codes: H04B 10/298 Two-way repeaters, i.e. repeaters amplifying separate upward and downward lines
• CPC Class Codes: H04B 2210/078 using a separate wavelength
• CPC Class Codes: H04B 2210/08 Shut-down or eye-safety

Abstract

An optical amplifier and an optical multiplexing transmission system using the same are disclosed. Automatic restoration of the operation becomes possible and malfunctioning of an APSD function is prevented. The optical amplifier using Raman amplification includes; a Raman excitation light source for generating Raman light; and a detection circuit for detecting a signal error in an OSC (optical supervisory channel) signal transmitted in addition to optical transmission signal. When the detection circuit detects a bit error in the OSC signal, an output power from Raman excitation light source is controlled so as not to injure the human body.

Claims

1. An optical amplifier using Raman amplification, comprising:

a Raman excitation light source generating Raman light;

a detection circuit detecting a code error, a frame error, and an optical supervisory channel (OSC) signal break on an OSC signal being transferred, in addition to an optical transmission signal; and

a controller increasing Raman light output power of a Raman excitation light source to a predetermined level when the code error and the frame error are detected by said detection circuit, and shutting down the Raman light output power at the OSC signal break.

2. The optical amplifier according to claim 1, further comprising:

a circuit for indicating a transmission line failure to a downstream optical amplifier by means of a flag superposed onto the optical supervisory channel (OSC) signal, which indicates an optical supervisory channel condition, when the errors detected by said detection circuit become a predetermined condition.

3. The optical amplifier according to claim 1, further comprising:

a light-output control circuit for supervising a flag, which indicates the optical supervisory channel (OSC) condition in each OSC signal received from an upstream transmission line concerned and from an upstream transmission line in the opposite direction to perform light output control.

4. The optical amplifier according to claim 3,

wherein said light-output control circuit controls to adjust light output power of the Raman excitation light source down to a level not dangerous to the human body.

5. The optical amplifier according to claim 3,

wherein said light-output control circuit controls the Raman excitation light source to completely cut off the light output power.

6. The optical amplifier according to claim 3,

wherein said light-output control circuit supervises the errors on the optical supervisory channel (OSC) signal, and removes the light output control against the Raman excitation light source, when said errors are restored to a predetermined condition.

7. The optical amplifier according to claim 3,

wherein said light-output control circuit removes the light output control against the Raman excitation light source depending on the flag indicated in said optical supervisory channel (OSC) signal.

8. An optical amplifier using Raman amplification, comprising:

a Raman excitation light source generating Raman light;

a detection circuit detecting errors on an optical supervisory channel (OSC) signal being transferred, in addition to an optical transmission signal;

a controller controlling Raman light output power of the Raman excitation light source according to the errors detected by said detection circuit; and

a light-output control circuit supervising a flag, which indicates an OSC condition in each OSC signal received from an upstream transmission line and from an upstream transmission line in the opposite direction to perform light output control,

wherein said light-output control circuit supervises the errors on the OSC signal, and removes the light output control against the Raman excitation light source when said errors are restored to a predetermined condition, and

wherein, when Raman light output control against said Raman excitation light source is removed, said light-output control circuit outputs to an optical fiber transmission line, Raman light producing Raman gain corresponding to a bandwidth of said OSC signal, awaits OSC line restoration, and outputs Raman light after said OSC signal is restored normally, to produce Raman gain in a wavelength required according to wavelength information indicated through said OSC line to remove said optical amplifier light output control.

9. The optical amplifier according to claim 8,

wherein, after said OSC signal is terminated at the equipment concerned, a flag indicating a condition of said optical supervisory channel (OSC) is transmitted back to upstream using an OSC signal through the opposite line.

10. The optical amplifier according to claim 9,

wherein said optical supervisory channel (OSC) signal is transmitted through a line having independent wavelengths in C-band and L-band.

11. An optical multiplexing transmission system having a plurality of optical amplifiers interconnected with multi-state cascade connections, each of the plurality of optical amplifiers comprising:

an optical amplifier amplifying light received from a transmission line;

a Raman excitation light source exciting the transmission line;

an error detection circuit detecting a code error, a frame error, and an optical supervisory channel (OSC) signal break on an OSC signal transmitted from upper stream of said optical amplifier;

a controlling circuit increasing Raman light output power produced in said Raman excitation light source to a predetermined level when said detection circuit detects the code error and the frame error in said OSC signal, and shutting down the Raman light output power at the OSC signal break; and

a circuit transmitting a flag downstream indicating said OSC signal condition from said optical amplifier.

12. The optical multiplexing transmission system according to claim 11 further comprising two lines consisting of an uplink and a downlink,

wherein each of the plurality of optical amplifiers terminates said optical supervisory channel (OSC) signal, and includes a circuit for transmitting a flag indicating an OSC line condition back to upstream through a line in the opposite direction.