Abstract: Optical signal to noise ratios that more accurately characterize optical link noise are determined. As noise induced by an optical receiver does not generally vary with an input optical signal power, a power of an incoming optical signal is varied at the receiver. A resulting variation in noise measure represents a variation in link noise and does not include any variation caused by receiver noise, as receiver noise does not generally vary with optical signal power. Thus, the contribution of optical link noise can be discerned from other noise induced by the receiver itself. A more accurate characterization of optical link performance is thus provided.

Abstract: Optical signal to noise ratios that more accurately characterize optical link noise are determined. As noise induced by an optical receiver does not generally vary with an input optical signal power, a power of an incoming optical signal is varied at the receiver. A resulting variation in noise measure represents a variation in link noise and does not include any variation caused by receiver noise, as receiver noise does not generally vary with optical signal power. Thus, the contribution of optical link noise can be discerned from other noise induced by the receiver itself. A more accurate characterization of optical link performance is thus provided.

Abstract: A system includes a laser configured to generate a tunable optical frequency. The system also includes an optical transmitter to map baseband data to symbols represented in a digital modulation constellation, add a frequency offset to the digital modulation constellation to cause the digital modulation constellation to rotate at a rate equal to the added frequency offset, modulate the optical frequency with the rotating digital modulation constellation, and transmit the resulting modulated optical frequency. The system also includes an optical receiver to receive the transmitted modulated optical frequency and, using the tunable optical frequency, detect the rotating digital modulation constellation conveyed by the received modulated optical frequency.

Abstract: A system includes a laser configured to generate a tunable optical frequency. The system also includes an optical transmitter to map baseband data to symbols represented in a digital modulation constellation, add a frequency offset to the digital modulation constellation to cause the digital modulation constellation to rotate at a rate equal to the added frequency offset, modulate the optical frequency with the rotating digital modulation constellation, and transmit the resulting modulated optical frequency. The system also includes an optical receiver to receive the transmitted modulated optical frequency and, using the tunable optical frequency, detect the rotating digital modulation constellation conveyed by the received modulated optical frequency.

Abstract: In an optical receiver, an optical local oscillator (LO) frequency is generated. A modulated optical frequency is received at the optical receiver. An LO-signal frequency offset between the received modulated optical frequency and the optical LO frequency is determined. A determination is made as to whether the LO-signal frequency offset is in one of multiple predefined non-overlapping target windows that cover respective non-zero LO-signal frequency offsets. If it is determined that the LO-signal frequency offset is not in one of the target windows, the optical LO frequency is tuned to drive the LO-signal frequency offset toward one of the target windows to ensure the LO-signal frequency offset is non-zero.

Abstract: In an optical receiver, an optical local oscillator (LO) frequency is generated. A modulated optical frequency is received at the optical receiver. An LO-signal frequency offset between the received modulated optical frequency and the optical LO frequency is determined. A determination is made as to whether the LO-signal frequency offset is in one of multiple predefined non-overlapping target windows that cover respective non-zero LO-signal frequency offsets. If it is determined that the LO-signal frequency offset is not in one of the target windows, the optical LO frequency is tuned to drive the LO-signal frequency offset toward one of the target windows to ensure the LO-signal frequency offset is non-zero.