Ciena Corporation

John H Brownlee

Donald J Miller

John P Mateosky

Jun Bao

Matthew William Connolly

Si Hyung Cho

Steven W Cornelius

Boris Kershteyn

Prasad Dasika

Robert Corwin

The present invention utilizes field programmable gate arrays (FPGAs) to implement a parallel differential quadrature phase shift keying (DQPSK) precoder and a DQPSK optical transmitter with an automatic realignment process. The present invention can perform DQPSK preceding, modulation, and data stream realignment at any lower rate, and its upper rate is determined by capability in speed and logic resources and external connections of available integrated circuit technology.

DQPSK transmitter with parallel precoder and high-speed DQPSK data stream realignment

The present invention provides a timing recovery architecture and circuit for recovering the clock timing from a received signal in critically-timed transport applications. The present invention further relates to a timing recovery architecture and circuit for removing network-induced clock jitter and wander that occurs in a transport network during asynchronous mapping techniques, bit and/or byte-stuffing techniques, or traditional pointer adjustment schemes associated with traditional PDH (pleisiosynchronous digital hierarchy), SDH (synchronous digital hierarchy), and packet-based networks. The timing recovery circuit may be implemented in a logic circuit such as programmable, digital FPGA (field programmable gate array) logic, or alternatively in standard cell or gate-array ASIC (application-specific integrated circuit) technology, or like logic circuit design.

System and method for an adaptable timing recovery architecture for critically-timed transport applications

The dynamic range of an optical amplifier is extended by the addition of a power control circuit. A switch is interposed between a current source and an optical pump supplying pumping light to the gain medium of the optical amplifier. A modulated signal such as a pulse-width modulated signal is used to actuate the switch and control a relative duration of the &ldquo;on&rdquo; and &ldquo;off&rdquo; periods of the electrical current supplied to the optical pump. Gain latency in the optical amplifier permits a substantially continuous signal to be output from the optical amplifier in response to the switched electrical current supply to the optical pump. A controller may used a feedback signal from the optical pump or from a power monitoring device to control the modulator and, thereby, the switch. A target pump power level, target gain or target amplified signal power level may also be applied in a feedback control loop that controls the modulator and switch. The invention also takes the form of a method that may be used to control a conventional optical amplifier in order to expand the dynamic range, particularly in the low power region.

Method and apparatus for expanding the dynamic range of optical amplifiers

A receiver node includes an optical amplifier optically coupled to the input of a receiving device such as a PIN photodiode. A controller inputs received power level values from the receiver to perform gain control. The input signal of an optical receiving device is pre-amplified by an optical amplifier such that the amplified signal is within a dynamic range of the receiving device. Upon the occurrence of a LOS (loss of signal) event, the controller sets the gain to a Home Gain value. Thus, when the signal is reestablished, a strong signal will not be over amplified and damage the receiver. Gain control is reestablished when the LOS event is over. Various methods are used to declare LOS including comparing the received power level or commanded pump power against a threshold. The LOS declaration may also be received from an external device or service channel.

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Tucker, GA, United States of America

John H Brownlee