Abstract: A system for optical communication forms a family of orthogonal optical codes modulated by a data stream. The orthogonal codes are formed by creating a stream of evenly spaced-apart pulses using a pulse spreader circuit and modulating the pulses in amplitude and/or phase to form a family of orthogonal optical code words, each representing a symbol. A spreader calibration circuit is used to ensure accurate timing and modulation. Each code word is further modulated by a predetermined number of data bits. The data modulation scheme splits a code word into H and V components, and further processes the components prior to modulation with data, followed by recombining with a polarization beam combiner. The data-modulated code word is then sent, along with others to receiver. The received signal is detected and demodulated with the help of a symbol synchronization unit which establishes the beginning and end of the code words.

Abstract: A system for optical communication send optical signals over a plurality of wavelength channels. Each wavelength channel comprises a number of orthogonal subchannel frequencies which are spaced apart from one another by a predetermined amount. Each of the subchannel frequencies is modulated with data from a data stream. The data modulation scheme splits a subchannel frequency code into H and V components, and further processes the components prior to modulation with data. The various data-modulated subchannels are then combined into a single channel for transmission. The received signals are detected and demodulated with the help of a symbol timing recovery module which establishes the beginning and end of each symbol. A polarization mode distortion compensation module at the receiver is used to mitigate the effects to polarization more distortion in the fiber.

Abstract: A system for optical communication send optical signals over a plurality of wavelength channels. Each wavelength channel comprises a number of orthogonal subchannel frequencies which are spaced apart from one another by a predetermined amount. Each of the subchannel frequencies is modulated with data from a data stream. The data modulation scheme splits a subchannel frequency code into H and V components, and further processes the components prior to modulation with data. The various data-modulated subchannels are then combined into a single channel for transmission. The received signals are detected and demodulated with the help of a symbol timing recovery module which establishes the beginning and end of each symbol. A polarization mode distortion compensation module at the receiver is used to mitigate the effects to polarization more distortion in the fiber.

Abstract: A system for optical communication forms a family of orthogonal optical codes modulated by a data stream. The orthogonal codes are formed by creating a stream of evenly spaced-apart pulses using a pulse spreader circuit and modulating the pulses in amplitude and/or phase to form a family of orthogonal optical code words, each representing a symbol. A spreader calibration circuit is used to ensure accurate timing and modulation. Each code word is further modulated by a predetermined number of data bits. The data modulation scheme splits a code word into H and V components, and further processes the components prior to modulation with data, followed by recombining with a polarization beam combiner. The data-modulated code word is then sent, along with others to receiver. The received signal is detected and demodulated with the help of a symbol synchronization unit which establishes the beginning and end of the code words.

Abstract: A frequency-domain analysis method computes noise power spectral densities (PSDs) in nonlinear circuits. The method uses harmonic components of the periodic time-varying PSD of cyclostationary noise, i.e., harmonic power spectral densities which are deterministic functions that describe the time-varying second-order statistics of cyclostationary noise. A block-structured matrix equation is used which relates output noise statistics to input noise statistics. By exploiting Toeplitz block structure, an efficient noise calculation method requires O(nN log N) computation time and O(nN) memory, where n is the circuit size and N is the number of significant harmonics in the circuit's steady state. The method successfully treats device noise sources with arbitrarily shaped PSDs (including thermal, shot, and flicker noises), handles noise input correlations and computes correlations between different outputs.

Abstract: Novel algorithms for computing the responses of circuits to multi-tone excitations. The new algorithms are efficient and robust for large, strongly nonlinear circuits excited by multi-tone (quasi-periodic or envelope-modulated) signals. Hence they are particularly useful for integrated RF applications. The multivariate representation captures features produced by strong nonlinearities (such as spikes or pulses) much more compactly than traditional frequency- or time-domain representations. The new algorithms compute these functions efficiently by solving a partial differential equation ODE) in the time or mixed frequency-time domains. Frequency-domain spectra or time-domain waveforms are generated from the multivariate functions as cheap post-processing steps. Two methods, multivariate FDTD and hierarchical shooting, are purely time-domain techniques suitable for the general strongly nonlinear circuit problem. They differ in their memory and computation needs.

Abstract: Systems and methods that include a homotopy technique are employed to find a DC operating point of large-scale, transistor-based, nonlinear circuits?, allowing such circuits to be designed, tested and manufactured!. The systems and methods use arclength continuation together with a new two-phase embedding of .lambda. into equations describing the circuits.

Abstract: Systems and methods for determining one or more characteristics of a singular circuit, allowing such circuits to be efficiently designed, tested and manufactured. One of the systems includes: (1) a minimum least-squares ("MLS") determination circuit that receives parameters relating to the singular circuit into a matrix A, determines range and null spaces for the matrix A, applies an orthonormalization procedure to determine a solution x to Ax=b', where b' is an orthogonal projection of a known vector b onto the range space of the matrix A and derives an MLS solution from the solution x and (2) a simulation circuit, coupled to the MLS determination circuit, that employs the MLS solution to simulate an operation of the singular circuit and determine the characteristic therefrom.