US 2017/0324476 A1 · Skew Measurement in an Optical Coherent Transponder

Abstract

Systems and methods for measuring the in-phase/quadrature (I/Q) skew of optical signals are disclosed. The method may be used to characterize the I/Q skew of optical signals transmitted by optical coherent transponders in complex modulation formats. The method may include providing an input signal to a transponder to produce a periodic (and generally sinusoidal) output signal, providing the output signal to a test system including an optical spectrum analyzer, measuring the optical power of a first harmonic of the signal, and comparing the measured optical power to calibration data to determine the I/Q skew. The optical power may be analyzed in a portion of the spectrum where sensitivity of the power to changes in skew is highest. The calibration data may map previously-obtained optical power measurements to corresponding known skew amounts. The system may provide more accurate skew measurements using less expensive equipment than existing skew measurement methods.

Claims20

Dependent claims

A method for measuring in-phase/quadrature skew, the method comprising:

providing, to an optical spectrum analyzer, an optical signal transmitted by an optical coherent transponder;
performing, using the optical spectrum analyzer, a measurement of optical power for a hail ionic of the optical signal with respect to a carrier of the optical signal;
determining an amount of in-phase/quadrature skew introduced by the optical coherent transponder dependent on a result of the measurement;
generating an indication of the determined amount of in-phase/quadrature skew introduced by the optical coherent transponder.

1 more element

A system, comprising:

an optical spectrum analyzer comprising circuitry to:
receive an optical signal transmitted by an optical coherent transponder under test;
and
perform a measurement of optical power for a harmonic of the optical signal with respect to a carrier of the optical signal;
and
a skew detector comprising circuitry to:
determine an amount of in-phase/quadrature skew introduced by the optical coherent transponder dependent on a result of the measurement;
and
generate an indication of the determined amount of in-phase/quadrature skew introduced by the optical coherent transponder.

6 more elements

A method for producing an optical coherent transponder, the method comprising:

communicatively coupling an optical coherent transponder built in accordance with a first design specification to a test system that includes an optical spectrum analyzer;
determining, dependent on a first measurement made by the optical spectrum analyzer, an amount of in-phase/quadrature skew introduced by the optical coherent transponder;
determining whether or not the amount of in-phase/quadrature skew introduced by the optical coherent transponder can be compensated for by circuitry within the optical coherent transponder;
and
in response to determining that the amount of in-phase/quadrature skew introduced by the optical coherent transponder cannot be compensated for in the optical coherent transponder:
modifying the optical coherent transponder in accordance with a second design specification;
communicatively coupling the modified optical coherent transponder to the test system;
determining, dependent on a second measurement made by the optical spectrum analyzer, an amount of in-phase/quadrature skew introduced by the modified optical coherent transponder;
and
determining whether or not the amount of in-phase/quadrature skew introduced by the modified optical coherent transponder can be compensated for by circuitry within the modified optical coherent transponder.

7 more elements

Dependencies are inferred from the claim text.

Skew Measurement in an Optical Coherent Transponder

Life of this patent

Skew Measurement in an Optical Coherent Transponder

Life of this patent

Abstract

Claims20