An optical end terminal in which protection switching is implemented by using (i) the optical data receiver thereof for detecting a path failure and (ii) the optical data transmitter thereof for signaling the detected path failure to the protection-switching circuit. In an example embodiment, the optical data receiver is configured to detect a path failure based on the presence of certain data-recovery errors. The optical data transmitter is operatively connected to the optical data receiver and configured to generate an in-band dither tone of a predetermined frequency in response to such failure detection. The protection-switching circuit is configured to (i) detect dither tones in the optical signals passing therethrough and (ii) connect the optical data receiver to the protection path instead of the working path in response to detecting the dither tone of the predetermined frequency.

An optical end terminal in which protection switching is implemented by using (i) the optical data receiver thereof for detecting a path failure and (ii) the optical data transmitter thereof for signaling the detected path failure to the protection-switching circuit. In an example embodiment, the optical data receiver is configured to detect a path failure based on the presence of certain data-recovery errors. The optical data transmitter is operatively connected to the optical data receiver and configured to generate an in-band dither tone of a predetermined frequency in response to such failure detection. The protection-switching circuit is configured to (i) detect dither tones in the optical signals passing therethrough and (ii) connect the optical data receiver to the protection path instead of the working path in response to detecting the dither tone of the predetermined frequency.

An optical transmission system including an optical transmission device and an optical reception device that receives, via an optical transmission line, a signal transmitted from the optical transmission device, the optical transmission system including a transmission-mode selection unit that selects transmission mode information in descending order of priority out of transmission mode information, which is combinations of a plurality of parameters concerning transmission performance, the transmission mode information being a plurality of kinds of the transmission mode information common to the transmission performance of the optical transmission device and the optical reception device, a signal transmission unit that transmits, to the optical reception device, a signal modulated based on the selected transmission mode information, and a signal reception unit that receives the signal and modulates the received signal based on the transmission mode information selected by the transmission-mode selection unit.

An optical transceiver can be calibrated using an internal receiver side eye scan generator, and calibration values (e.g., modulator values) can be stored in memory for recalibration of the optical transceiver. The eye scan generator can receive data from the transmitter portion via an integrated and reconfigurable loopback path. At a later time, different calibration values can be accessed in memory and used to recalibrate the optical transceiver or update the calibrated values using the receive-side eye scan generator operating in loopback mode.

A test device and method for testing a distributed feedback laser diode (DFB-LD) device for an optical transceiver of a radio over fiber (RoF) system examines the DFB-LD device based on an absolute limiting rating, an operating case environment, and a functional specification, in which the absolute limiting rating is a rating at which there is no fatal damage to the DFB-LD device during a short period of time when each limiting parameter is isolated and all other parameters are in a normal performance parameter, the operating case environment includes an operating temperature, and the functional specification includes parameters to be tested according to an operating condition for the functional specification.

A test device and method for testing a distributed feedback laser diode (DFB-LD) device for an optical transceiver of a radio over fiber (RoF) system examines the DFB-LD device based on an absolute limiting rating, an operating case environment, and a functional specification, in which the absolute limiting rating is a rating at which there is no fatal damage to the DFB-LD device during a short period of time when each limiting parameter is isolated and all other parameters are in a normal performance parameter, the operating case environment includes an operating temperature, and the functional specification includes parameters to be tested according to an operating condition for the functional specification.

A skew compensation system for a coherent optical communication network includes a transmitter modulator having a first driver input for receiving a first signal from a first channel, a second driver input for receiving a second signal from a second channel, a source input for receiving a continuous wave source signal, and a modulation output in communication with an optical transport medium of the network. The system further includes a tunable delay line disposed between the second channel and the second driver input for inserting a pre-determined training sequence onto the second signal prior to the second driver input, and a processor for determining a skew amount between the second signal at the second driver input and the first signal at the first driver input, calculating a pre-compensation value corresponding to the skew amount, and reducing the skew amount at the modulation output according to the pre-compensation value.

A method is provided for calibrating a terminal device connected to a transmission line containing an impairment. The method includes steps of obtaining a sequence of frequency domain samples for a digital signal transmitted to the terminal device, determining a reflection coefficient from the obtained frequency domain sequence and a reflection signal arising from the impairment, converting the sequence of frequency domain samples and the frequency domain reflection signal into the time domain to generate a complex time domain sample sequence having a real I time component and an imaginary Q time component, correcting the time domain sample sequence into a corrected time sequence having a phase value of the Q component corresponding to a phase value of the I component, calculating a correcting spin coefficient from the corrected time sequence, and calibrating the terminal device with the correcting spin coefficient to mitigate a rotation of the reflection coefficient.

According to the present example embodiment, the optical fiber sensing system is an optical fiber sensing system being acquired by adding a function of optical fiber sensing to a cable of an optical communication cable system. The optical communication cable system includes the cable including an optical fiber core wire that propagates an optical signal for communication, and a plurality of devices. A function of the optical fiber sensing is a function of, by an interrogator, sending probe light to an optical fiber core wire, detecting backscattered light of the probe light, and performing sensing on environmental information around the cable. The device includes an optical wiring line through which sensing light passes without passing through an optical amplifier.

An optical system (100) is described including: a reconfigurable optical device (103) with multiplexing wavelength division, comprising a plurality of actuators (A1-AN) and having associated a number of optical channels (M) and a number of degrees of freedom (N) lower than the number of optical channels; an optical stimulus source (106) connected to said reconfigurable optical device (103) to provide an optical stimulation signal (S.sub.in) having a wavelength band including a plurality of wavelengths associated with the optical channels; an optical-electric conversion device (200) configured to receive from said reconfigurable optical device (103) an optical monitoring signal (S.sub.out) corresponding to the optical stimulation signal (S.sub.in) and to provide a group of electrical signals of intensity (S.sub.EL1-S.sub.ELK) each representative of an intensity of the optical monitoring signal (S.sub.out) evaluated at a relative wavelength included in said band. The system also includes a control device (110) configured to control the plurality of actuators (A1-AN) according to said group of electrical signals (S.sub.EL1-S.sub.ELK) and according to a control law.