Optical time domain reflectometer (OTDR) with improved dynamic range and linearity
First Claim
Patent Images
1. An optical time-domain-reflectometer (OTDR), comprising:
- a pulse generator for launching optical pulses into an optical component under test, said pulses exhibiting pulse widths in a range of nanoseconds to microseconds and being launched at repetition rates in a range of about 0.1 to 50 kHz,a receiver, such as an avalanche photodiode detector, with a specific bandwidth, for receiving a backscatter signal of said optical component under test and for generating a first electrical signal representative of said backscatter signal and a first noise signal,an amplifier for amplifying said first electrical signal and said first noise signal,noise source means for generating a second noise signal and combining said first electrical signal and first noise signal, after amplification thereof by said amplifier, with said second noise signal, and outputting combined signals,an analog-digital-converter (ADC) with a sampling frequency fS for converting the combined signals to first digital data, andmeans for averaging said first digital data and for removing digital data corresponding to said second noise signal.
4 Assignments
0 Petitions
Accused Products
Abstract
This invention relates to a method and an apparatus for performing exceptionally linear averaging of digitized signals in an optical time domain reflectometer. Resolutions far below the quantization level of the ADC with improved linearity can be achieved without sacrificing dynamic range. Such method can be used to improve measurement accuracy on optical fibers under test.
43 Citations
12 Claims
-
1. An optical time-domain-reflectometer (OTDR), comprising:
-
a pulse generator for launching optical pulses into an optical component under test, said pulses exhibiting pulse widths in a range of nanoseconds to microseconds and being launched at repetition rates in a range of about 0.1 to 50 kHz, a receiver, such as an avalanche photodiode detector, with a specific bandwidth, for receiving a backscatter signal of said optical component under test and for generating a first electrical signal representative of said backscatter signal and a first noise signal, an amplifier for amplifying said first electrical signal and said first noise signal, noise source means for generating a second noise signal and combining said first electrical signal and first noise signal, after amplification thereof by said amplifier, with said second noise signal, and outputting combined signals, an analog-digital-converter (ADC) with a sampling frequency fS for converting the combined signals to first digital data, and means for averaging said first digital data and for removing digital data corresponding to said second noise signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. Method for time domain reflectometry, comprising:
-
a first step in which an optical backscatter signal of an optical component under test is received and a first electrical signal representative of said backscatter signal and a first noise signal are generated, a second step in which said first electrical signal and said first noise signal are amplified, a third step in which a second noise signal is generated and superposed with the amplified first electrical signal and the amplified first noise signal, a fourth step in which the superposed signals are sampled at a frequency fS, and are converted to first digital data, a fifth step in which said first digital data is averaged, and thereafter a sixth step in which digital data corresponding to said second noise signal is removed from said first digital data. - View Dependent Claims (12)
-
Specification