Systems and methods for calibrating a ring modulator are described. A system may include a controller configured to provide a first test signal to the ring modulator, determine a first candidate temperature control signal for a heater of the ring modulator when the first test signal is provided to the ring modulator, determine a first optical swing of an optical signal at a drop port of the ring modulator, determine a second candidate temperature control signal for the heater when the first test signal is provided to the ring modulator, determine a second optical swing of an optical signal at the drop port, select an optimal optical swing from the first optical swing and the second optical swing, and select one of the first candidate temperature control signal or the second candidate temperature control signal based on the optimal optical swing selected.

Examples described herein relate to calibration of an optical communications link. Data signals received over the optical communications link are measured to obtain an eye scan. A height of an upper eye region and a height of a lower eye region are compared in the eye scan. A common mode calibration value is adjusted based on any difference in the heights. A common mode adjustment circuit is then controlled based on the common mode calibration value. The common mode adjustment circuit is configured to remove a direct current bias within a receiver for the optical communications link.

A light source outputs a light. A branching unit branches the light output from the light source into a first branched light and a local oscillation light. A modulator modulates the first branched light to output an optical signal. A receiver causes the local oscillation light to interfere with an optical signal to receive the optical signal. An EDFA amplifies the optical signal output from the modulator. An excitation light source outputs an excitation light exciting the EDFA to the EDFA. An optical attenuator attenuates optical power of the optical signal amplified by the EDFA. A control unit controls attenuation of the optical signal in the optical attenuator. The control unit adjusts the attenuation of the optical signal and adjusts an output of the excitation light from the excitation light source.

Embodiments are disclosed for generating a lookup table value for calibrating a lookup table circuit in an optical transmitter. The example method includes generating a calibration signal. The calibration signal encodes a plurality of bits in a number of amplitude levels. The example method further includes transmitting the calibration signal to a module under calibration and transmitting a symbol sequence of defined length to a reference module. The reference module compares the symbol sequence with a distorted signal received from the module under calibration to generate a set of condition count statistics. The example method further includes receiving the set of condition count statistics from the receiver in the reference module and calculating a lookup table value based on the set of condition count statistics. The example method further includes transmitting the lookup table value to a transmitter associated with the module under calibration.

An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at a test modulation frequency F. COR performance parameters are determined by comparing two frequency components of the COR output. CMRR is determined based on a strength of a direct detection spectral line at the modulation frequency relative to that of spectrally-shifted lines at (Ff). GDV information is obtained by modulating one of the lights at two phase-locked frequencies, such as F and 2F, and comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two frequencies.

Test equipment that is able to concurrently evaluate two or more optical modules each processing a wavelength multiplexed signal that multiplexes optical signals attributed to wavelengths different from each other. The test equipment provides a first test station and a second test station. After selecting one of the wavelengths, the first test station performs a first evaluation for an optical signal attributed to the one of the wavelengths and coming from the first optical module, and the second station concurrently performs a second evaluation for an optical single with the one of the wavelengths and coming from the second optical module. Thereafter, the first test station performs the first evaluation for the optical signal coming from the second optical module, while, the second test station performs the second evaluation for the optical signal coming from the first optical module.

Improvements in extinguishing optical signals in silicon photonics may be achieved by supplying a test signal of a known characteristics to a Photonic Element (PE) to extinguish the test signal via a first phase shifter and intensity modulator on a first arm of the PE and a second phase shifter and intensity modulator on a second arm of the PE; sweeping through a plurality of voltages at the first intensity modulator to identify a first voltage that is associated with an extinction ratio at an output of the PE that satisfies an induced loss threshold and a second voltage that is associated with an induced loss in the test signal at the output of the PE that satisfies an extinction ratio threshold; and setting the PE to provide an operational voltage to the first intensity modulator based on the first voltage and the second voltage.

To provide a method and device capable of easily measuring the CMRR vs. frequency characteristics of an optical receiver. Light having a measurement frequency ( [hz]) is split into two different paths, and a first optical two-tone signal, which is signal light and has a frequency difference ( [hz]), and a second optical two-tone signal, which is local light and has a frequency difference (+ [hz]), are obtained and input into a coherent receiver to be measured, wherein electrical signals output from the receiver are measured to obtain both the ratio of the intensity of a signal component having the frequency [hz] to the intensity of a signal component having the frequency [hz], which corresponds to the CMRR on the signal light side, and the ratio of the intensity of a signal component having the frequency + [hz] to the intensity of the signal component having the frequency [hz], which corresponds to the CMRR on the local light side.

According to examples, a fiber-optic testing source for testing a multi-fiber cable may include a laser source communicatively coupled to a plurality of optical fibers connected to a connector. The fiber-optic testing source may include at least one photodiode communicatively coupled to at least one of the plurality of optical fibers by at least one corresponding splitter to implement a communication channel between the fiber-optic testing source and a fiber-optic testing receiver. The communication channel may be operable independently from a polarity associated with the multi-fiber cable. The fiber-optic testing receiver may include a plurality of photodiodes communicatively coupled to a plurality of optical fibers. The fiber-optic testing receiver may include at least one laser source communicatively coupled to at least one of the plurality of optical fibers by at least one corresponding splitter to implement the communication channel between the fiber-optic testing receiver and a fiber-optic testing source.

There is provided a method, system and image capture device for determining a polarity of a multi-fiber cable link comprising a plurality of optical fiber links each connected between a first multi-fiber connector and a second multi-fiber connector, according to said polarity. Test light is injected into one or more of the optical fiber links via corresponding injection ports of the first multi-fiber connector, in accordance with a defined injection pattern; at least one polarity-testing image of the second multi-fiber connector is generated in which test light exiting at least one of the optical fiber links through one or more exit ports of the second multi-fiber connector is imaged as one or more spotlight spots in the polarity-testing image; and the polarity of the multi-fiber cable link is determined based on a pattern of said one or more spotlight spots in said polarity-testing image.