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.

In one embodiment, information passing mechanism between the two connected optical transceivers is provided. Within the first optical transceiver, Rx 1 calculates the current condition of the uplink channel and passes this information together with the condition of the downlink channel that it receives from Tx 2 to Tx 1. The Tx 1 uses the downlink channel condition that it receives from the Rx 1 to generate signal with appropriate modulation format, shaping factor, baudrate and coding scheme for maximizing the downlink's capacity. The Tx 1 then transmits this information together with the uplink channel condition received from Rx 1 to Rx 2. The Rx 2 uses the information about the modulation format, baudrate, shaping factor and coding scheme that it receives from Tx 1 for the reception of information-bearing signal. The Rx 2 then calculates the transmission channel condition of the downlink channel and passes this information together with the uplink channel condition that it receives from Tx 1 to Tx 2. The Tx 2 then uses the uplink channel condition that it receives from the Rx 2 to generate signal with optimized modulation format, shaping factor, baudrate and coding scheme for maximizing the uplink's capacity. The information exchange process between the two connected optical transceivers then repeats in an endless loop.

A communication apparatus includes a plurality of devices, each of the plurality of devices includes a monitoring unit configured to monitor at least one other device to detect an error that has occurred in the other device, and each of the plurality of devices is monitored by at least one other device.

An optical signal processing method, a control unit, an optical transmission unit and a storage medium are disclosed. The optical signal processing method includes: acquiring an OSNR value from an optical receiving unit (S100); acquiring a spectrum shaping adjustment parameter according to the OSNR value (S200); and sending the spectrum shaping adjustment parameter to an optical transmission unit to adjust a filtering parameter of a shaping filter of the optical transmission unit, so that the optical transmission unit adjusts a spectrum waveform of an optical signal by utilizing the shaping filter after adjustment (S300).

Systems and methods for controlling network configurations or assignments are provided. A method, according to one implementation, includes a step of calculating transmission characteristics between each pair of a plurality of pairs of modems at opposite ends of a Dense Wavelength-Division Multiplexing (DWDM) transport link using specifications of the modems measured during production. The method also includes the step of selecting a pair of modems from the plurality of pairs of modems based on results obtained by calculating the transmission characteristics and based on one or more user-defined service requests.

Controller circuitry configured to control an optical transceiver of an optical line terminal, OLT, in a passive optical network, PON. The controller circuitry configured to derive a level of optical beat interference, OBI, of a received upstream optical signal from an optical transceiver of an optical network terminal, ONT; and set a wavelength of a downstream optical signal based on the level of OBI such that the wavelength is forced to differ from the upstream optical signal wavelength.

A system for estimating an imbalance between electrical-optical responses of an in-phase (I) channel and a quadrature (Q) channel in an optical amplitude and phase modulator (optical IQ modulator) includes an optical detector (PD), an analog-digital converter (ADC), and an imbalance operation unit that estimates an imbalance between electrical-optical responses of an I channel and a Q channel in the optical IQ modulator, wherein the imbalance operation unit includes an input signal information receiving unit that receives information regarding a first modulation signal, and an intensity information receiving unit that receives intensity information of the digitalized output signal from the ADC, and the imbalance operation unit estimates an imbalance between electrical-optical responses of an I channel and a Q channel in the optical IQ modulator using information regarding a first modulation signal and intensity information of the digitalized output signal.

An OLT 110 includes an optical transmission/reception unit 111 to transmit and receive optical signals by time division; an abnormal-light-emission detection unit 112 to monitor the received optical signals, and detect a state in which the optical signals are being received for a predetermined period or longer as abnormal light emission in which the optical signals from one or more of the ONUs 130 are not received; an optical-communication control unit to sequentially select an ONU 130 one at a time from the plurality of ONUs 130 other than the one or more ONUs 130 as a target ONU 130, test whether the abnormal light emission is resolved by stopping transmission of the optical signal from each target ONU 130, and, if the abnormal light emission is resolved, specifies the target ONU 130 being tested as an ONU 130 that is a source of the abnormal light emission.

A communication device includes: an optical-communication circuit that is capable of performing optical communication with a different communication device and transmits a first electric signal to the different communication device at a startup time of the communication device; an electro-communication circuit that is capable of performing electro communication with the different communication device and receives a second electric signal transmitted from the different communication device in response to the first electric signal; and a control circuit that transmits error information indicating an error in the optical communication to a device after the second electric signal is received by the electro-communication circuit.

An optical transmitter has an optical modulator having Mach-Zehnder interferometers, modulator drivers configured to drive the optical modulator by a drive signal, a low frequency generator configured to generated a low frequency signal that changes a ratio of a driving amplitude with respect to a half-wave voltage of the optical modulator, a photodetector configured to detect a portion of output light of the optical modulator, a detector configured to detect a low frequency component contained in a detected signal from the photodetector using the low frequency signal, and a bias voltage controller configured to control a bias voltage for the optical modulator such that the detected low frequency component becomes the maximum and in-phase with the superimposed low frequency signal.