A multi-level optical signal is sampled to generate an eye diagram. The signal can be adjusted when eyes in the eye diagram have different heights. More specifically, a first value is determined, and the height of a first eye is adjusted using the first value. The first value is multiplied by a stored factor to produce a second value, and the height of a second eye is adjusted using the second value, and so on for other eyes. As a result, eye heights are the same. Similarly, optical power levels of the signal can be adjusted when the levels are not equally spaced. As a result, the optical power levels are equally spaced.

A test device tests conditions associated with a fronthaul in an Open Radio Access Network (O-RAN). The test device can field test an O-RAN radio unit (O-RU) installed at a cell site by emulating an O-RAN distributed unit (O-DU) in the O-RAN connected to the O-RU via the fronthaul of the O-RAN. The testing includes testing connectivity of the O-RU to the fronthaul. The testing includes executing managing plane (M-plane) and synchronization plane (S-plane) messaging to test management session establishment, device setting testing, and master clock synchronization testing. Additionally, optical insertion loss in the fronthaul and frequency and power of signals transmitted from the O-RU can be tested.

Provided is an optical transceiver including: a controller configured to output firmware update data for updating firmware of another optical transceiver connected to the optical transceiver through an optical cable; and a transmitter configured to generate an optical signal by superposing input payload data and the firmware update data, and to transmit the optical signal to the other optical transceiver. According to embodiments, the firmware of a remote optical transceiver at a remote location is automatically updated without affecting payload data, which is information to be transmitted.

A multi-level optical signal is sampled to generate an eye diagram. The signal can be adjusted when eyes in the eye diagram have different heights. More specifically, a first value is determined, and the height of a first eye is adjusted using the first value. The first value is multiplied by a stored factor to produce a second value, and the height of a second eye is adjusted using the second value, and so on for other eyes. As a result, eye heights are the same. Similarly, optical power levels of the signal can be adjusted when the levels are not equally spaced. As a result, the optical power levels are equally spaced.

A signal pre-compensation method is provided. In the method, at least one target frequency subband is determined from a plurality of frequency subbands of a first optical signal and an optical signal of the at least one target frequency subband in the first optical signal is demodulated based on the at least one target frequency subband. A first electrical signal is obtained after demodulation, and a pre-compensation parameter is updated based on the at least one target frequency subband, the first electrical signal, and a second electrical signal. Herein the pre-compensation parameter is used to perform signal pre-compensation on the second electrical signal, and the first optical signal is generated after the pre-compensation is performed on the second electrical signal.

A method and system is described. A signal indicative of a failure of a first channel within a plurality of channels of a transmission signal traversing a signal working path in a network is received. The signal working path has a headend node, a tail-end node and an intermediate node. The first channel has a frequency band and a power level prior to failing. The signal working path is associated with a protection path. The protection path includes the intermediate node, optical cross-connects, and a transmitter supplying (ASE) light. The transmitter is activated to supply the ASE light within a frequency band and having a power level corresponding to the frequency band and power level associated with the first channel. The ASE light is supplied to a cross-connect, such that the cross-connect provides a transmission signal including the ASE light.

An ONU includes a communication unit, an abnormal light emission prevention unit, and a control unit that transmits a data signal and a transmission permission signal to the communication unit and transmits the transmission permission signal to the abnormal light emission prevention unit between a transmission start time and a transmission end time. When the transmission permission signal is received, the communication unit, transmits an optical signal to an OLT, and transmits an operation signal to the abnormal light emission prevention unit during the transmission of the optical signal. The abnormal light emission prevention unit transmits a stop signal to the communication unit when a difference between a time for which the transmission permission signal is received and a time for which the operation signal is received is greater than or equal to a threshold value. The communication unit stops when the stop signal is received.

The disclosed systems and methods for optical filter fault localization. The optical filter fault localization is based on: i) determining an accumulated noise density at frequencies where ASE noise is filtered out by a faulty optical filter in an optical signal; ii) comparing the accumulated noise density with predicted accumulated noise densities, the predicted accumulated noise densities representing noises predicted from a plurality of optical filters to a receiver; and iii) determining, based on the comparison of the accumulated noise density and the predicted accumulated noise densities, a location of the faulty optical filter.

An optical transmitter device includes a modulator of the Mach-Zehnder type that modulates the optical signal from an emitter and outputs modulated signals; and a phase controller that controls the phase difference of the modulator according to a setting phase amount. The device includes a controller, a sweeper, and an estimator. The controller controls the bias current of the emitter so that the power of the modulated signals detected at the output stage of the modulator during the optical shutdown becomes the target value during the optical shutdown. After the bias current is controlled, the sweeper performs constant-period sweeping of the phase of the modulator. The estimator estimates, while sweeping the phase, the transmission characteristics of the modulator from the power of the optical signal detected at the input stage of the modulator; and, from the estimated characteristics, calculates the optimum phase amount to be set in the phase controller.

A communication device is provided that estimates one or more disturbance values associated with one or more components of the communication device, and adjusts the communication device to change a received power of the output signal. The communication device includes a transmitter having a seed laser configured to provide an amount of bandwidth for an output signal, an Erbium-doped fiber amplifier (EDFA) configured to increase an amplitude of the output signal, and a single mode variable optical attenuator (SMVOA) configured to decrease the amplitude of the output signal.