Fujitsu Corporation

Infinera Corporation

Emilio Bravi

Ramakrishna Pratapa

Qian Liang

Methods and apparatuses for restoring lost signal in a network transmission line are disclosed. A first optical signal transmitted from a first optical module is received at an optical switch, the first optical signal having a first optical spectrum with data encoded into the first optical signal. A second optical signal having a second optical spectrum corresponding to the first optical spectrum without data encoded into the second optical signal, is received at the optical switch, the second optical signal the second optical signal transmitted from an amplified spontaneous emission source. Detecting, at a first photo detector, a loss of optical spectrum in the first optical signal, and, in response to detecting the loss of optical spectrum in the first optical signal, switching the optical switch from passing the first optical signal to passing the second optical signal thereby supplying at least one idler carrier without data imposed.

Methods and apparatuses to mitigate multicarrier failure for submarine optical links

Optical networks, nodes and methods are disclosed. To solve the aggressor issue and to reduce the cross-talk caused by the aggressors in colorless, directionless and contentionless reconfigurable optical add drop multiplexer nodes, the present disclosure configures a first broadcast module to supply only non-adjacent wavelengths to a first input port of a wavelength selective switch, and a second broadcast module to supply only non-adjacent wavelengths to a second input port of the wavelength selective switch.

Apparatus and method to reduce the impact of coherent crosstalk in optical networks

Optical networks, transponders and single-laser coherent transceiver are described. The single-laser coherent transceiver includes a wavelength source, a transmitter and a receiver. The wavelength source is tuned to supply a first optical signal having a first wavelength. The transmitter receives the first optical signal and encodes client data into the first optical signal to generate a second optical signal. The receiver receives the first optical signal from the wavelength source and a fraction of the second optical signal.

Apparatus and method to improve optical reach in bidirectional optical transmission systems employing single-laser coherent transceivers

Systems and methods for measuring the in-phase/quadrature (I/Q) skew of optical signals. 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.

Skew measurement in an optical coherent transponder

Systems and methods for detecting and correcting bias errors in optical coherent transponders are disclosed. An 'outer' modulator in a transponder may, when properly biased, produce a phase offset of &#x3c0;/2 radians between in-phase and quadrature components of the optical signals transmitted in optical modulation formats by the transponder. The method may include providing input to a transponder to produce a periodic (and generally sinusoidal) output signal, measuring (using an optical power meter) 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, and determining that a curve representing the measurements performed on the positive harmonics and a curve representing the measurements performed on the negative harmonics are not orthogonal. The method may include adjusting the bias voltage of the modulator to make the two curves orthogonal, thus eliminating the bias error.

Bias error correction in an optical coherent transponder

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.

Skew compensation in an optical coherent transponder

Methods and systems for transient gain cancellation at an optical amplifier may involve generating saturating light that is introduced in a reverse direction to a transmission direction at a doped fiber amplification element. The doped fiber amplification element may amplify an input optical signal having a plurality of wavelengths as well as the saturating light. The saturating light may be regulated by a control circuit to counteract transient gain effects of add/drop events in the input optical signal. The saturated light may be filtered to achieve a desired spectral profile.

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Hillsdale, NJ, United States of America

Emilio Bravi