Abstract:
A system and method including polarization modulation of supervisory signals for reducing interference with data signals in a wavelength division multiplexed optical communication system. At least one supervisory signal for monitoring a transmission path [102] and/or elements coupled to the transmission path [102] is fast polarization modulated and launched with data signals onto the path. Polarization modulating [402] of the supervisory signal reduces impact of the supervisory signal on the data signals and improves system performance.
Abstract:
An optical transceiver in an optical communications network, comprising a receiver configured to receive an optical signal comprising an X-polarization component and a Y-polarization component. The optical transceiver further comprises a processor coupled to the receiver and configured to determine a chromatic dispersion (CD) estimate and a local oscillator frequency offset (LOFO) estimate based on a relationship between a plurality of CD values and a plurality of LOFO values. The optical transceiver further comprises a transmitter coupled to the processor and configured to transmit the CD estimate, the LOFO estimate, and the optical signal to a downstream component in the optical communications network.
Abstract:
According to an example aspect, there is provided an apparatus comprising a first optical converter coupled to a fibre interface and to two waveguides, a dual rail encoder configured to encode dual rail form light from the two waveguides with payload information, and wherein the dual rail encoder is coupled to the first optical converter or to a second optical converter disposed between the dual rail encoder and the fibre interface, and wherein the first optical converter or the second optical converter is coupled so as to provide polarization encoded light into the fibre interface.
Abstract:
A method (1400) for dual polarization coherent optical modulation includes: mapping (1401) data bits to a first constellation according to a first modulation format to provide first constellation data bits; mapping (1402) the first constellation data bits to a second constellation according to a second modulation format to provide second constellation data bits, wherein the second constellation comprises a higher number of constellation points than the first constellation; and modulating (1403) the second constellation data bits onto a dual polarized optical signal, wherein the optical signal comprises a first polarization component (X) and a second polarization component (Y).
Abstract:
An optical transmitter configured to mitigate the adverse effects of fiber nonlinearity by altering the transmitted constellation symbols based on specific nonlinear characteristics of a fiber- optic link over which the optical transmitter is configured to transmit and on an a priori estimate of the nonlinear component of the optical- signal distortion in that fiber-optic link. In an example embodiment, each constellation symbol is altered by a respective perturbation amount determined using (i) a calculated or measured nonlinear transfer function corresponding to the fiber-optic link and (ii) a set of neighboring constellation symbols that are expected to contribute to the nonlinear distortion of the optical signal carrying the present constellation symbol due to the fiber nonlinearity. In various embodiments, different appropriate perturbation amounts can be selected to approximately pre-compensate nonlinear distortions caused by various nonlinear optical effects, such as four-wave mixing, etc.
Abstract:
A method of optical communication comprising encoding four modulated symbols to generate four encoded symbols in two orthogonal polarizations and transmitting the four encoded symbols in two successive time slots. An optical communication apparatus comprising a processor configured to receive two sequences of digital symbols in a plurality of time slots, wherein the two sequences correspond to two components of two orthogonal polarizations, wherein one digital symbol per polarization is received in each of the plurality of time slots, divide each of the two sequences into a plurality of groups using a modulo operation of time, wherein each group comprises two digital symbols received in two consecutive time slots, and adaptively equalize the four digital symbols of the two consecutive time slots using a 4x4 matrix to generate four modulated symbols, wherein the 4x4 matrix comprises 16 tap-vectors.
Abstract:
Proposed is a method of optical data transmission. The method comprises different steps. A first optical signal and a second optical signal are generated, such that the optical signals possess a same wavelength, respective phases, which are modulated in dependence on respective data values, and respective polarization states, which are essentially orthogonal to each other. A combined optical signal is generated, by combining the optical signals, such that the combined optical signal possesses a polarization state with a predetermined variation. The combined optical signal is transmitter over an optical transmission line and received. Two time-discrete sampled signals are generated, by sampling the received optical signal along two orthogonal polarization planes. Two filtered signals are generated, by filtering the time-discrete sampled signals in the time-discrete domain, using a function that is indicative of the respective predetermined variation. Finally, respective data values are derived from the filtered signals.