Systems and methods for connection validation between a pair of mated transceivers implemented in a network element include, responsive to a request for connection validation at a first transceiver of the pair of mated transceivers, performing a first optical loopback test through the first transceiver with a unique trace identifier; responsive to a successful first optical loopback test, providing the unique trace identifier to a second transceiver of the mated transceivers with a request for a second optical loopback test; performing the second optical loopback test through the second transceiver with the unique trace identifier; and, responsive to a successful second optical loopback test, providing the unique trace identifier back to the first transceiver from the second transceiver.

A transmission apparatus being one of a plurality of transmission apparatuses included in a ring network, including: a processor configured to: receive a specified message from a first transmission apparatus, the specified message being for setting loopback for at least one wavelength in a ring network, the specified message being transmitted when a failure of at least one optical signal having the at least one wavelength is detected in a specified link of the ring network, and set a loopback to a switch, the loopback being set for a specified wavelength of the at least one wavelength when a specified optical signal having the specified wavelength is terminated by the switch and converted to an electrical signal and when the specified optical signal having the specified wavelength is not terminated and not converted to an electrical signal by any apparatus from a second transmission apparatus to the specified link.

A transmission apparatus being one of a plurality of transmission apparatuses included in a ring network, including: a processor configured to: receive a specified message from a first transmission apparatus, the specified message being for setting loopback for at least one wavelength in a ring network, the specified message being transmitted when a failure of at least one optical signal having the at least one wavelength is detected in a specified link of the ring network, and set a loopback to a switch, the loopback being set for a specified wavelength of the at least one wavelength when a specified optical signal having the specified wavelength is terminated by the switch and converted to an electrical signal and when the specified optical signal having the specified wavelength is not terminated and not converted to an electrical signal by any apparatus from a second transmission apparatus to the specified link.

Systems, methods, and devices are disclosed for monitoring optical communications between a managed location and a remote location. In particular, an optical signal is transmitted over an optical fiber and passed-through a test device. A portion of the optical signal is filtered from the original optical signal and passed to a monitoring unit. The monitoring unit may instruct one or more switches in the test device to loop the optical signal back toward the managed location. Subsequently, testing and monitoring may be performed at the managed location. The device may provide a test output or may transmit the information to the managed location.

Systems, methods, and devices are disclosed for monitoring optical communications between a managed location and a remote location. In particular, an optical signal is transmitted over an optical fiber and passed-through a test device. A portion of the optical signal is filtered from the original optical signal and passed to a monitoring unit. The monitoring unit may instruct one or more switches in the test device to loop the optical signal back toward the managed location. Subsequently, testing and monitoring may be performed at the managed location. The device may provide a test output or may transmit the information to the managed location.

Modulated optical signals are received in a coherent optical receiver employing both post digital filter and inter-symbol-interference (ISI) equalizer such as a maximum likelihood sequence estimation (MLSE) or Bahl-Cocke-Jelinek-Raviv (BCJR) algorithms. Some disclosed techniques are directed to adaptively adjusting the impulse response in time domain (or equivalently the frequency response in frequency domain) of the post digital filter and the corresponding structure of ISI equalizer in different spectrum-narrowing operation scenarios.

Dynamic error-quantizer tuning systems and methods prevent misconvergence to local minima by using a dynamic quantizer circuit that controls reference voltages of three or more comparators that are independently adjusted to modify the transfer function of the dynamic quantizer circuit. A weighted sum of the comparator outputs is subtracted from the input to form an error signal in a control loop. The ratio of the reference voltages is chosen to reduce or eliminate local minima during a convergence of the control loop and is set to values that minimize a mean squared error signal with respect to discrete modulation states of the input after the convergence of the control loop is complete.

Dynamic error-quantizer tuning systems and methods prevent misconvergence to local minima by using a dynamic quantizer circuit that controls reference voltages of three or more comparators that are independently adjusted to modify the transfer function of the dynamic quantizer circuit. A weighted sum of the comparator outputs is subtracted from the input to form an error signal in a control loop. The ratio of the reference voltages is chosen to reduce or eliminate local minima during a convergence of the control loop and is set to values that minimize a mean squared error signal with respect to discrete modulation states of the input after the convergence of the control loop is complete.

A communications device is disclosed and includes: a first acquiring unit for acquiring first specific wavelength light and second specific wavelength light from a first optical path; a first receiving unit for converting the first specific wavelength light coming from the first acquiring unit into a first electrical signal; a first control unit for sending a first modulating signal to a first loopback unit according to the first electrical signal coming from the first receiving unit; and the first loopback unit for modulating the second specific wavelength light coming from the first acquiring unit according to the first modulating signal, and looping the modulated second specific wavelength light back to a second optical path, where a transmission direction of an optical signal in the second optical path is opposite to a transmission direction of an optical signal in the first optical path. The present invention further discloses a communications method.

A communications device is disclosed and includes: a first acquiring unit for acquiring first specific wavelength light and second specific wavelength light from a first optical path; a first receiving unit for converting the first specific wavelength light coming from the first acquiring unit into a first electrical signal; a first control unit for sending a first modulating signal to a first loopback unit according to the first electrical signal coming from the first receiving unit; and the first loopback unit for modulating the second specific wavelength light coming from the first acquiring unit according to the first modulating signal, and looping the modulated second specific wavelength light back to a second optical path, where a transmission direction of an optical signal in the second optical path is opposite to a transmission direction of an optical signal in the first optical path. The present invention further discloses a communications method.