Optical communication systems include optical time domain reflectometers that are coupled to link fibers to determine link fiber lengths. After length measurement, chromatic dispersion associated with the measured length is estimated. In some examples, the estimated chromatic dispersion is compensated. A single OTDR can be used to assess a pair of link fibers coupling first and second network nodes by injecting a probe pulse at a common end of the link fibers or by routing the probe pulses from a remote end of one link fiber into a remote end of a second fiber.

Methods and systems for optical signal transmission, particularly with carrier-less amplitude and phase (CAP) modulation and direct detection, are disclosed. In one exemplary aspect, a method of optical signal transmission is disclosed. The method includes receiving information bits at an input interface; mapping the information bits to a plurality of modulation symbols; separating in-phase (I) and quadrature (Q) components of the plurality of modulation symbols such that the I and Q components form a Hilbert pair in a resulting signal; pre-dispersing the resulting signal with an inverse of a phase delay of an expected chromatic dispersion to obtain a pre-dispersed signal; converting the pre-dispersed signal from digital domain to analog domain using a digital to analog conversion circuit; performing modulation of an output of the digital to analog conversion circuit to generate an output signal; and transmitting, over an optical transmission medium, the output signal from the modulation.

An optical dispersion compensator integrated with a silicon photonics system including a first phase-shifter coupled to a second phase-shifter in parallel on the silicon substrate characterized in an athermal condition. The dispersion compensator further includes a third phase-shifter on the silicon substrate to the first phase-shifter and the second phase-shifter through two 22 splitters to form an optical loop. A second entry port of a first 22 splitter is for coupling with an input fiber and a second exit port of a second 22 splitter is for coupling with an output fiber. The optical loop is characterized by a total phase delay tunable via each of the first phase-shifter, the second phase-shifter, and the third phase-shifter such that a normal dispersion (>0) at a certain wavelength in the input fiber is substantially compensated and independent of temperature.

Optical fiber data communications are described. A controller can determine chromatic dispersion of an optical signal that is to be demodulated using coherent detection. The controller can then determine the chromatic dispersion of another optical signal that is to be demodulated using direct detection. The chromatic dispersion of the other optical signal can then be adjusted to account for chromatic dispersion experienced by the other optical signal when it propagated through an optical fiber.

The present invention relates to performing chromatic dispersion estimation in a receiver of an optical communication system. Here, the signal received by the receiver includes frames, each comprising a training portion and a data portion. The training portion comprises a plurality of identical pattern sequences. Different settings are applied to an equalizer to generate a plurality of equalized signals from at least one of the received frames. Then, at least one correlation value is calculated between a first pattern sequence and a second pattern sequence of the equalized signals and a final correlation value is derived from the respective correlation values. The setting of the equalizer corresponding to the equalized signal providing the highest final correlation value is selected to provide the chromatic dispersion estimation.

Aspects of a method and system for feedback during optical communications are provided. In one embodiment, a system for optical communications comprises a predistortion module, a feedback subsystem, a transmit optical subsystem, and an external modulator. The predistortion module is operable to receive an input digital signal and modify the input digital signal to produce a digital predistorted signal. The transmit optical subsystem is operable to generate an optical signal from the digital predistorted signal. The modification of the input digital signal is dynamically controlled by the feedback subsystem according to one or more characteristics of the optical signal as determined by the feedback subsystem. The amplitude of the external modulator output is also dynamically controlled by the feedback subsystem.

There is provided a transmission apparatus including a transmitter configured to modulate a signal to a first signal having a first wavelength and a signal to a second signal having a second wavelength, and transmit the first signal and the second signal to a transmission line so that the second signal is varied in accordance with variation in an amount of cross phase modulation of the first signal passing through each position on the transmission line, and a signal processor configured to include at least one of a logic device and a processor, and configured to add an amount of chromatic dispersion at which a remaining amount of chromatic dispersion of the first wavelength at a certain position on the transmission line is equal to zero to the first wavelength in the transmission of the first signal and the second signal.

The disclosure discloses a Chromatic Dispersion (CD) detection method for an optical transmission network. Data of two polarization states orthogonal to each other is converted from time-domain data to frequency-domain data, extraction is performed on the frequency-domain data and a linear combination operation is performed on the extracted frequency-domain data, an argument of a CD value of the data of the two polarization states are obtained according to a result of the linear combination operation, and the CD value is estimated according to the argument of the CD value of the data of the two polarization states. The disclosure further discloses a CD detection device for the optical transmission network and a storage medium.

An optical transceiver configured to operate in a host device includes an electrical interface communicatively coupled to the host device to interface electrically with the host device, wherein the optical transceiver is compliant with a Multi-Source Agreement (MSA) which is supported by the host device; optical transceiver components communicatively coupled to the electrical interface, wherein the optical transceiver components are configured to optically interface signals with a second optical transceiver to form an optical link; and electronic dispersion compensation circuitry communicatively coupled to the optical transceiver components and configured to electronically compensate for optical fiber chromatic and/or polarization mode dispersion associated with the optical link, separate and independent from the host device.

An optical dispersion compensator integrated with a silicon photonics system including a first phase-shifter coupled to a second phase-shifter in parallel on the silicon substrate characterized in an athermal condition. The dispersion compensator further includes a third phase-shifter on the silicon substrate to the first phase-shifter and the second phase-shifter through two 22 splitters to form an optical loop. A second entry port of a first 22 splitter is for coupling with an input fiber and a second exit port of a second 22 splitter is for coupling with an output fiber. The optical loop is characterized by a total phase delay tunable via each of the first phase-shifter, the second phase-shifter, and the third phase-shifter such that a normal dispersion (>0) at a certain wavelength in the input fiber is substantially compensated and independent of temperature.