Ciena Corporation

Harshad P Sardesai

Michael Y Frankel

Balakrishnan Sridhar

Jun Bao

Vipul Bhatnagar

Charles Haggans

Mahir A Nayfeh

Michael George Taylor

Vladimir S Grigoryan

Shan Zhong

John J Veselka, Jr

Yunfeng Shen

Sanjaykumar Upadhyay

Steve Sluz

The present disclosure provides systems and methods for channel power offsets for multi-rate dense wave division multiplexed (DWDM) transmission over optical add-drop multiplexers (OADMs). The present invention includes algorithms to set power levels of each type of channel in different sections of a fiber system to optimize the performance of that type of channel at the receiver. For example, the present invention can optimize power levels based on different channel modulation formats, bit rates, channel spacings, and the like. Advantageously, the present invention improves the total capacity (bit rate) and reach that channels of a given bit rate can achieve, and maximizes the reach of channels without sacrificing capacity.

Systems and methods for channel power offsets for multi data rate DWDM transmission over optical add drop multiplexers

The present invention provides systems and methods for highly efficient bit error rate (BER) modeling in quasi-linear communication networks. In the present invention, nonlinear noise is treated within a linearization approach along with the amplified spontaneous emission (ASE) noise, and the nonlinear noise is considered as another source of noise in addition to the ASE noise. This enables a quasi-analytical approach to the BER calculation. First, a covariance matrix is analytically computed. An equation is derived for a noise component of a signal and an implicit analytical solution is found depending on the signal and system parameters. Second, probability distribution functions (pdfs) are computed for the signal. An analytical calculation is performed of the characteristic function for the noise statistics. Next, a numerical computation of the Fourier transform of the characteristic function is performed to yield the pdf, and numerical integration is performed on the pdfs to yield the BER.

Systems and methods for highly efficient bit error rate modeling in quasi-linear communication networks

The present disclosure provides polarization mode dispersion compensation (PMDC) and polarization de-multiplexing systems and methods for polarization multiplexed (PolMux) optical transmission systems. The PMDC detects an error signal before a polarization splitter in PolMux systems for controlling polarization controllers (PC) and/or DGDs in the PMDC for return-to-zero (RZ) differential m-phase shift keying (DmPSK) signals. For bit-aligned PolMux systems, the error signal could be the level of clock frequency at one, two, or more times of the baud rate at one polarization. For bit-interleaved PolMux systems, the error signal could be the level of clock frequency at two times of the baud rate at one polarization. The PMDC can operate in PolMux systems with any arbitrary time offset between the two polarizations. The polarization de-multiplexer utilizes error detection at both output arms of a polarization splitter to mitigate PDL impact on any PolMux type of signal.

Polarization mode dispersion compensation and polarization demultiplexing systems and methods for optical transmission systems

Chromatic dispersion in a high speed CS-RZ WDM transmission system is reduced by providing tailored 'precompensation' for individual and/or groups of optical signals. Such precompensation is achieved by passing the optical signals through a dispersion compensating elements, such as dispersion compensating fiber, within an optical multiplexer, i.e., prior to multiplexing the signals onto a single optical fiber. Additional dispersion compensation can be performed in optical amplifiers and within an optical demultiplexer downstream from the optical multiplexer.

WDM system having chromatic dispersion precompensation

A method and apparatus for controlling phase alignment in a modulator of a transmitter in an optical communications system utilizes an RF power signature to tune phase alignment. A portion of the optical signal is tapped and converted to an electrical signal. An electrical band-pass filter and RF detector examines a narrow slice of the RF spectrum and utilize the detected RF power to control phase alignment between the data modulator and pulse carver. Another portion of the optical signal is multiplied by the pulse carver clock, filtered and integrated in order to generate a second phase control signal for controlling the relative phase of a dual arm modulator being used as the pulse carver in one embodiment.

Method and apparatus for controlling modulator phase alignment in a transmitter of an optical communications system

A optical communications network including at least one optical phase conjugator for compensating for non-linear effects. The optical communications network includes at least one dispersion compensation module before the optical phase conjugator and at least one dispersion compensation module after the optical phase conjugator. The dispersion compensation modules compensate for linear effects of the transmission path such as dispersion and dispersion slope. This allows the optical phase conjugator to be designed to compensate for non-linear effects such as self-phase modulation and cross-phase modulation. The separate compensation of linear and non-linear effects provides enhanced control of these effects.

Method and system for using optical phase conjugation in an optical communications network

A method and system for compensating residual dispersion curvature in an optical communication network is disclosed. One embodiment employs two types of dispersion compensating fiber to reduce higher order terms in a residual dispersion profile. The two types of dispersion compensating fiber may be co-located in a dispersion compensation module positioned in each transmission fiber link. Alternatively, the two types of dispersion compensating fiber may be distributed across a span of the optical communication network.

Method and system for compensating residual dispersion curvature

A method and system for using optical phase conjugation in an optical communications network including an add-drop multiplexer. The method includes determining a position for an optical phase conjugator such that channel quality for a channel in improved above a threshold. Transmission characteristics such as amplifier launch power or dispersion features may be adjusted to compliment the optical phase conjugation. An alternate method includes positioning the optical phase conjugator to improve a weighted average channel quality for the network.

Method and system for using optical phase conjugation in an optical communications network including an add/drop multiplexer

An optical communication device, and related method, are provided for reducing ripple in WDM systems. In particular, the optical communication device includes a dynamic gain equalization (DGE) circuit is coupled to an optical communication path carrying the WDM optical signals. The DGE circuit adjusts the powers associated with each channel on a channel-by-channel basis so that the WDM optical signal has a desired power spectrum. The DGE is controlled in response to sense signals generated by an optical performance monitoring (OPM) circuit located downstream from the DGE or substantially co-located with the DGE. The OPM monitors the WDM spectrum for optical signal power variations and outputs the sense signal when the variations fall outside a given tolerance. Typically, one DGE is associated with a group of concatenated amplifiers so that multiple DGEs are provided in a system having many groups of such amplifiers. Likewise, multiple OPMs are provided in such systems, each corresponding to a respective DGE, so that ripple can be reduced and desired WDM optical signal powers can be achieved in the WDM system.

Optical communication system having dynamic gain equalization

In a wavelength division multiplexed system, optical frequencies are assigned in accordance with a channel plan conforming to an International Telecommunications Union (ITU) grid whereby every third channel position in the grid is vacant. As a result, both four wave mixing (FWM) and cross phase modulation (XPM) are reduced using ITU standard frequencies. In addition, a low bandwidth expansion factor (BEF) can be achieved.

Wavelength division multiplexed optical communication system having reduced non-linear effects

A dispersion compensating element having a substantially uniform spectral nonlinearity is described. The dispersion compensating unit is thus suitable for incorporation into high speed wavelength division multiplexed (WDM) optical communication systems. Several examples of dispersion compensating elements are discussed, each of which comprising at least one segment of dispersion compensating fiber.

Dispersion compensating element having substantially uniform spectral nonlinearity

Consistent with the present invention, in-fiber Bragg gratings are used to demultiplex optical signals in a WDM optical communication system. The in-fiber Bragg gratings also perform dispersion compensation of the selected optical signals. As a result, additional segments of DCF for further dispersion compensation are rendered unnecessary. Improved performance is thus achieved with an inexpensive and simplified system design.

WDM optical communication system having a dispersion slope compensating element

In accordance with the present invention, a dispersion compensation module is coupled to a transmission optical fiber. The dispersion compensation module includes segments of optical fiber of varying length, some of which have a positive dispersion while other have a negative dispersion. Selected optical fiber segments are coupled to one another to provide a desired net dispersion to offset the dispersion associated with the transmission optical fiber. Thus, rather than provide a unique segment of DCF for each span, the same dispersion compensation module can be used for spans of varying length and fiber types by simply connecting appropriate segments of fiber within the module.

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Elkridge, MD, United States of America

Harshad P Sardesai