USE OF LINEAR SCATTERING LOSSES TO CHARACTERIZE AMPLIFIED FIBER SPANS

• US 20040095569A1
• Filed: 11/20/2002
• Published: 05/20/2004
• Est. Priority Date: 11/20/2002
• Status: Abandoned Application

• Current Assignee: Innovance Inc.
• Original Assignee: Innovance Inc.
• Inventors: Kan, Clarence Kwok-Yan
• Application Number:
  US10/300,156
• Publication Number:
  US 20040095569A1
• Time in Patent Office: Days
• US Class Current: 356/73.1
• CPC Class Codes: H01S 3/0014 Monitoring arrangements not otherwise provided for photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003
• CPC Class Codes: H01S 3/302 in an optical fibre
• CPC Class Codes: H04B 10/07 Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems

Abstract

A method is presented for calculating the Rayleigh backscattered signal (RBS) for an inhomogeneous fiber span amplified by a counter-propagating pump source, the fiber span being a concatenation of sections of different types of fiber. The method may be used to determine the Raman gain coefficients of each fiber section within the inhomogeneous fiber span. In addition, when the Raman gain coefficients for the fiber types are known, the method may be used to determine the fiber type of a section, if unknown.

Claims

1. A method for determining the Raman gain coefficient for a fiber section of an inhomogeneous fiber span provided with a Raman pump unit, comprising:

obtaining loss measurements at a location on said fiber section specified by a distance “

/”

from a signal source;

determining an on/off Raman gain G_on/off based on said loss measurements; and

determining the Raman gain coefficient of said fiber section at said specified location.

5. A method as claimed in claim 1, wherein said determining the Raman gain coefficient comprises calculating said gain coefficient “

g”

using

6. A method as claimed in claim 1, further comprising using fiber-Raman gain coefficient tables for determining the fiber type of said fiber section based on said Raman gain coefficient.

2. A method as claimed 1, wherein said loss measurements comprise a Rayleigh backscattered signal RBS.

3. A method as claimed in claim 2, wherein said step of measuring comprises:

with said Raman pump unit “

off”

,

measuring the power of the RBS at a nominal pump wavelength, to determine a pump loss value P_r⁰;

measuring the RBS power at a test signal wavelength P_r^W; and

with said Raman pump unit “

on”

at said nominal pump wavelength,

measuring the RBS power at said signal wavelength P_r^W |P_p⁰=0.

4. A method as claimed in claim 3, wherein said step of determining an on/off Raman gain G_on/off comprises dividing P_r^W to P_r^W |P_p⁰=0.