An information processing apparatus includes an optical transceiver configured to return an optical signal received by a first channel to a second channel at a time of immediate power disconnection of a casing accommodating nodes; a memory; and a processor coupled to the memory, wherein the processor detects an occurrence of a failure in inter-node communications with an external node, when the occurrence of a failure is detected, the processor controls the optical transceiver in order to emit light to the first channel, makes a determination as to whether or not the second channel is enabled to receive the optical signal, and determines whether or not a power source of the external node is off based on the determination, and when the power source of the external node is off, the processor selects a failure notification to transmit to a failure management device.

Apparatus and methods may provide improved equalizer performance, e.g., for optical-fiber-based communication systems. A least-mean-square (LMS) equalizer may include a decision feedback path containing feedback carrier recovery (FBCR), which may have low latency, and which may thus enable high-speed tap updating in the equalizer. Feed-forward carrier recovery (FFCR) may be applied, in parallel with the FBCR, to provide equalizer output by compensating, e.g., for phase noise, with improved carrier recovery/compensation, versus using FBCR to generate the output.

Apparatus and methods may provide improved equalizer performance, e.g., for optical-fiber-based communication systems. A least-mean-square (LMS) equalizer may include a decision feedback path containing feedback carrier recovery (FBCR), which may have low latency, and which may thus enable high-speed tap updating in the equalizer. Feed-forward carrier recovery (FFCR) may be applied, in parallel with the FBCR, to provide equalizer output by compensating, e.g., for phase noise, with improved carrier recovery/compensation, versus using FBCR to generate the output.

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.

Systems, methods, and storage media for detecting a security intrusion of a network device are disclosed. Exemplary implementations may include a method involving, in the network device including a processor, monitor a light signal associated with a security enabled port of the network device; and in response to detecting a change in the light signal, initiate a security alert.

Systems, methods, and storage media for detecting a security intrusion of a network device are disclosed. Exemplary implementations may include a method involving, in the network device including a processor, monitor a light signal associated with a security enabled port of the network device; and in response to detecting a change in the light signal, initiate a security alert.

Optical transceivers comprising optical loopback circuits are described. The optical transceiver may comprise a housing, which may host a transmitter, a receiver and the optical loopback circuit. The optical loopback circuit may be configured to route at least a portion of a modulated optical signal from the transmitter to the receiver. The optical loopback circuit may comprise tap couplers and/or optical switches. The optical transceiver may be switched between a normal mode and a calibration mode. The optical transceiver may maintain the same fiber connections even when the optical transceiver is switched from one mode to another. The transmitter, the receiver and the optical loopback circuit may be disposed on a common substrate, or on separate substrates.

Optical transceivers comprising optical loopback circuits are described. The optical transceiver may comprise a housing, which may host a transmitter, a receiver and the optical loopback circuit. The optical loopback circuit may be configured to route at least a portion of a modulated optical signal from the transmitter to the receiver. The optical loopback circuit may comprise tap couplers and/or optical switches. The optical transceiver may be switched between a normal mode and a calibration mode. The optical transceiver may maintain the same fiber connections even when the optical transceiver is switched from one mode to another. The transmitter, the receiver and the optical loopback circuit may be disposed on a common substrate, or on separate substrates.

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.