Abstract: Data throughput rates are increased in an optical fiber communication system without requiring replacement of the existing optical fiber in a link. Channel throughput is increased by upgrading the components and circuitry in the head and terminal of an optical fiber communication system link. Aggregate throughput in a fiber optic link is increased beyond the range of conventional Wavelength Division Multiplexed (WDM) upgrades, while precluding the necessity of replacing existing fiber plants. The increase in system throughput is achieved by using advanced modulation techniques to encode greater amounts of data into the transmitted spectrum of a channel, thereby increasing the spectral efficiency of each channel. This novel method of increasing transmission capacity by upgrading the head and terminal of the system to achieve greater spectral efficiency and hence throughput, alleviates the need to replace existing fiber plants.

Abstract: Decreasing the average transmitted power in an optical fiber communication channel using multilevel amplitude modulation in conjunction with Pulse Position Modulation (PPM). This multilevel PPM method does not entail any tradeoff between decreased power per channel and channel bandwidth, enabling a lower average transmitted power compared to On/Off Keying (OOK) with no reduction in aggregate data rate. Therefore, multilevel PPM can be used in high-speed Dense Wavelength Division Multiplexed (DWDM) systems where the maximum number of channels is traditionally limited by nonlinear effects such as self-phase modulation (SPM), cross-phase modulation (XPM), four-wave mixing (FWM), stimulated Brillouin scattering (SBS), and stimulated Raman scattering (SRS). This modulation technique can enable an increased number of channels in DWDM systems, thereby increasing aggregate data rates within those systems.

Abstract: A circuit can process a sample of a signal to emulate, simulate, or model an effect on the signal. Thus, an emulation circuit can produce a representation of a real-world signal transformation by processing the signal according to one or more signal processing parameters that are characteristic of the real-world signal transformation. The emulation circuit can apply analog signal processing and/or mixed signal processing to the signal. The signal processing can comprise feeding the signal through two signal paths, each having a different delay, and creating a weighted sum of the outputs of the two signal paths. The signal processing can also (or alternatively) comprise routing the signal through a network of delay elements, wherein a bank of switching or routing elements determines the route and thus the resulting delay.

Abstract: Signals propagating on an aggressor communication channel can cause detrimental interference in a victim communication channel. A signal processing circuit can generate an interference cancellation signal that, when applied to the victim communication channel, cancels the detrimental interference. The signal processing circuit can dynamically adjust or update two or more aspects of the interference cancellation signal, such as an amplitude or gain parameter and a phase or delay parameter. Via the dynamic adjustments, the signal processing circuit can adapt to changing conditions, thereby maintaining an acceptable level of interference cancellation in a fluctuating operating environment. A control circuit that implements the parametric adjustments can have at least two modes of operation, one for adjusting the amplitude parameter and one for adjusting the phase parameter. The modes can be selectable or can be intermittently available, for example.

Abstract: Signals propagating in one communication channel can generate crosstalk interference in another communication channel. A crosstalk cancellation device can process the signals causing the crosstalk interference and generate a crosstalk cancellation signal that can compensate for the crosstalk when applied to the channel receiving crosstalk interference. The crosstalk cancellation device can include a model of the crosstalk effect that generates a signal emulating the actual crosstalk both in form an in timing. The crosstalk cancellation device can include a controller that monitors crosstalk-compensated communication signals and adjusts the model to enhance crosstalk cancellation performance. The crosstalk cancellation device can have a mode of self configuration or calibration in which defined test signals can be transmitted on the crosstalk-generating channel and the crosstalk-receiving channel.

Abstract: Signals propagating in one communication channel can generate crosstalk interference in another communication channel. A crosstalk cancellation device can process the signals causing the crosstalk interference and generate a crosstalk cancellation signal that can compensate for the crosstalk when applied to the channel receiving crosstalk interference. The crosstalk cancellation device can include a model of the crosstalk effect that generates a signal emulating the actual crosstalk both in form an in timing. The crosstalk cancellation device can include a controller that monitors crosstalk-compensated communication signals and adjusts the model to enhance crosstalk cancellation performance. The crosstalk cancellation device can have a mode of self configuration or calibration in which defined test signals can be transmitted on the crosstalk-generating channel and the crosstalk-receiving channel.

Abstract: A receiver that can include an adaptive equalizer and a comparator processes communication signals that have been distorted by a propagation medium. The adaptive equalizer can correct for distortion of the received signals. The comparator can accept the equalized signal from the equalizer and quantize this signal. A control loop coupled to the equalized signal and the quantized signal can adjust the equalizer. The control loop can adjust the equalizer so that the high frequency energy in the equalized signal approximates the high-frequency energy in the quantized signal, taking into account variation between the low-frequency energies of these two signals.