US 2017/0324475 A1 · Skew Compensation in an Optical Coherent Transponder

Abstract

Systems and methods for reducing total skew in optical signals transmitted by optical coherent transponders without measuring the total skew are disclosed. The method may compensate for the in-phase/quadrature (I/Q) skew of optical signals in complex modulation formats. It may include providing input to a transponder to produce a periodic (and generally sinusoidal) output signal, providing the signal to an optical power meter, measuring the optical power of positive and negative harmonics of the signal while varying the amount of skew introduced by a de-skewing filter in the transponder, identifying the amount of skew introduced by the de-skewing filter when the minimum optical power measurement is taken, and causing the amount of skew introduced by the de-skewing filter to equal the identified skew offset by a one-half symbol delay. The system may provide better skew compensation using less expensive equipment than de-skewing methods based on existing skew measurement methods.

Claims20

Dependent claims

A method for reducing in-phase/quadrature (I/Q) skew error in an optical coherent transponder, the method comprising:

performing a plurality of measurements of optical power of harmonics of an optical signal transmitted by the optical coherent transponder, each measurement being taken while a respective different amount of skew is introduced into the optical signal by a de-skewing filter of the optical coherent transponder;
identifying a minimum optical power value obtained during the plurality of measurements of optical power;
determining an amount of skew that was introduced by the de-skewing filter when the minimum optical power value was obtained;
modifying the optical coherent transponder to cause the amount of skew introduced by the de-skewing filter to be substantially equal to:
the amount of skew that was introduced by the de-skewing filter when the minimum optical power value was obtained plus an amount of skew representing a one-half symbol delay;
or
the amount of skew that was introduced by the de-skewing filter when the minimum optical power value was obtained minus an amount of skew representing a one-half symbol delay.

4 more elements

A system, comprising:

circuitry to:
receive optical signals transmitted by an optical coherent transponder under test;
an optical power meter comprising circuitry to:
perform a plurality of measurements of optical power of harmonics of an optical signal transmitted by the optical coherent transponder under test, each measurement to be taken while a respective different amount of skew is introduced into the optical signal by a de-skewing filter of the optical coherent transponder;
a skew compensator comprising circuitry to:
identify a minimum optical power value obtained during the plurality of measurements of optical power;
determine an amount of skew that was introduced by the de-skewing filter when the minimum optical power value was obtained;
and
modify the optical coherent transponder to cause the amount of skew introduced by the de-skewing filter to be substantially equal to:
the amount of skew that was introduced by the de-skewing filter when the minimum optical power value was obtained plus an amount of skew to represent a one-half symbol delay;
or
the amount of skew that was introduced by the de-skewing filter when the minimum optical power value was obtained minus an amount of skew to represent a one-half symbol delay.

9 more elements

Dependencies are inferred from the claim text.

Skew Compensation in an Optical Coherent Transponder

Life of this patent

Skew Compensation in an Optical Coherent Transponder

Life of this patent

Abstract

Claims20