Infinera Corporation

Harmonic Lightwaves, Inc.

Infineria Corporation

Smith, Robert W., Jr.

Nilsson, Alan C.

Freeman, Paul N.

Kagan, Yishai

Alan C Nilsson

Robert B Taylor

Fred A Kish, Jr

David F Welch

Charles H Joyner

Radhakrishnan L Nagarajan

Vincent G Dominic

Matthew L Mitchell

Stephen G Grubb

Mark Missey

Richard P Schneider

Atul Mathur

Jonas Webjorn

Drew Daniel Perkins

Frank H Peters

Paul Nathan Freeman

Robert W Smith

Ting-Kuang Chiang

Frank Peters

Marco Sosa

Masaki Kato

Steven Joseph Hand

Peter Weindel Evans

Jeffrey Thomas Rahn

Ilya Lyubomirsky

Daniel P Murphy

Yishai Kagan

Chien-Yu Kuo

Parmijit Samra

Robert L Taylor

Kuang-Tsan Wu

James Edward Stewart

Mehrdad Ziari

Brian Taylor

David Piehler

Huan-Shang Tsai

Donald J Pavinski

Jeffrey Bostak

Fred A Kish

Robert Grencavich

Konstantin Saunichev

Charles H Gall

Vinh D Nguyen

Donald J Pavinski, Jr

Xingyu Zou

Joseph Kleefeld

Alfred Nicholson Riddle

Sanjeev Murthy

Harry Chou

Xinghua Yang

Mark J Missey

Marco E Sosa

Consistent with an aspect of the present disclosure, an optical communication apparatus is provided that transmits a WDM signal including a plurality of optical channels, wherein each channel has a corresponding one of a plurality of wavelengths. Each of the plurality of optical channels includes optical signals having first (e.g., TE) and second (e.g., TM) polarizations. In one example, each polarized optical signal is modulated in accordance with an identifying tone. The optical channels are combined onto a waveguide, and an optical tap connected or coupled to the waveguide supplies a portion of the WDM signal including a composite of the optical channels to a photodiode. The aggregate power received by the photodiode includes the power associated with each optical channel, and the power of each channel is the sum of the powers of individual polarized optical signals within that channel. The photodiode converts the received WDM portion including the polarized optical signal portions into corresponding electrical signals. A processor circuit demodulates the electrical signals, identifies the tones, and determines a modulation depth for each tone. Based on the modulation depth, a ratio of the optical powers of one polarized optical signal to another can be calculated, and the optical powers of one or both of the polarized optical signals in each channel can be adjusted so that the optical power ratio has a desired value, e.g., a value substantially equal to one. Thus, one tap and one photodiode may be provided to monitor each polarized optical signal within each WDM channel, thereby reducing costs and yielding a simpler system design.

Power control of optical signals having different polarizations

An optical system may include a polarization beam splitter having an input that receives multiple optical signals, a first output and a second output. The first output may provide components of the multiple optical signals having a first polarization. The second output may provide components of the multiple optical signals having a second polarization. The optical system may include a rotator having an input that receives the components to rotate the first polarization such that each of the components has the second polarization, and an output to supply components as rotated components. The optical system may also include an optical circuit including a substrate. The rotator may be separate from the substrate. The optical circuit may include an optical demultiplexer circuit provided on the substrate to receive the rotated components and the components.

Rotator external to photonic integrated circuit

A coherent optical transmitter circuit is disclosed in which controlled chirp is employed, enabling the suppression of nonlinear polarization scattering in dual polarization coherent systems, such as those which employ dual polarization-quadrature phase-shift keying (DP-QPSK). By separately chirping the modulated signals of each polarization tributary signal, the polarization state of the output DP-QPSK signal varies during a time period corresponding to a symbol bit period. Such controlled variations in the output DP-QPSK signal result in the mitigation of nonlinear effects associated with the network infrastructure over which the signal is transmitted, resulting in enhanced system performance. Enhanced system performance, for example, can be seen in greater reach and improved signal quality of the transmitted signal.

Controlled depolarization using chirp for mitigation of nonlinear polarization scattering

A power monitoring and correction to a desired power level of a laser or group of lasers utilizes two photodetectors which are employed to accurately determine the amount of output power from the front end or 'customer' end of a laser or a plurality of such lasers. During power detection, which may be accomplished intermittently or continuously, the laser is modulated with a tone of low frequency modulation. One photodetector at the rear of the laser is employed to detect the DC value of the frequency tone, i.e., a value or number representative of the AC peak-to-peak swing, amplitude or modulation depth of the tone. Also, the rear photodetector may be employed to determine the optical modulation index (OMI). In either case, these values may be employed in a closed loop feedback system to adjust or otherwise calibrate the value of the low tone frequency relative to the total desired bias current applied to the laser. A front photodetector is employed to receive a portion of the total output of the laser, or of each laser, and the average output power of the laser, or of each laser, is determined from already knowing the optical modulation index (OMI) via the rear photodetector. Thus, by measuring and/or calibrating the laser OMI with the use of a rear photodetector, the average output power from the front end output can be unambiguously determined from detection of the AC peak-to-peak swing or amplitude of the low frequency tone received via the front photodetector.

Monitoring of a laser source with front and rear output photodetectors to determine frontal laser power and power changes over laser lifetime

Optical autodiscovery is provide between two optical modules to insure that when an optical signal is coupled between the two optical module, the optical signal from a first module does not interfere with operation of a second module. The autodiscovery is implemented by sending an optical identification signal from the first optical module via the coupling to the second optical module from which signal, the second optical module can verify and determined acceptance of the coupled first optical module. During this autodiscovery process, the optical identification signal from the first optical module may be attenuated or shifted in optical spectrum so as not to interfere with the operation of the second optical module. Autodiscovery may also be employed in cases where a first optical module is to receive an optical signal from a second module.

Optical autodiscovery for automated logical and physical connectivity check between optical modules

Consistent with the present disclosure, an optical receiver is paired with an optical transmitter in a transceiver card or module, for example. During normal operation, the optical transmitter supplies optical signals for downstream transmission on a first optical communication path, and the optical receiver receives additional optical signals from a second optical communication path. During a transmitter monitoring mode (or 'loopback'), however, when monitoring of transmitter parameters is desired, an optical switch directs the output or portion thereof from the transmitter to the receiver. The receiver may then supply monitoring data or information to a control or processor circuit, which, in turn, may supply control signals to the transmitter. In response to such control signals, the performance of the transmitter may be optimized, for example, by reducing BER and/or OSNR to a desired level. The switch is then configured to block transmission of the transmitter output or portion and normal operation is commenced. Thus, consistent with the present disclosure, an optical receiver is provided to detect optical signals inbound on one optical communication path during normal operation is also used to receive optical signals directly from the transmitter during the monitoring mode. Accordingly, a dedicated monitoring receiver is not required and the system is rendered less expensive, power consumption may be minimized and space may be conserved.

Method and apparatus for local optimization of an optical transmitter

Consistent with the present disclosure, polarized optical signals having the same wavelength are modulated in response to ERZ drive signals, to thereby yield corresponding RZ optical signals. Each of the polarized RZ optical signals includes a plurality of RZ transitions wherein the power of the optical signal returns to zero or a minimal power between bits or symbols. The phase or timing of the ERZ drive signals, however, is controlled, so that the RZ transitions in one polarized optical signal remain interleaved with the RZ transitions of the other polarized optical signal. Alternatively, the RZ transitions of the two polarized optical signals may be controlled so that the two are temporally aligned with one another. Thus, the timing of the RZ transitions of one polarized optical signal relative to the other polarized optical signal may be adjusted to optimize system performance.

System for generating optical RZ signals based on electrical RZ signals

Consistent with the present disclosure, optical devices are provided along different optical paths in a photonic integrated circuit (PIC). The optical components have different optical losses associated therewith so that optical signals propagating in the optical paths have desired power levels, which may be uniform, for example.

Photonic integrated circuits having chirped elements

Consistent with the present disclosure, a transmitter is provided that includes first and second stages of wavelength locking circuitry. The first stage includes a tunable optical filter that sweeps through the spectrum of a WDM signal at a predetermined rate. A first photodiode senses a tapped portion of the output of the tunable filter. The remaining light is fed to the second stage, which includes a second optical filter, typically having a fixed transmission characteristic. A second photodiode senses the light that passes through the second filter. By sweeping the WDM spectrum the tunable filter can be used to identify the peaks in the WDM spectrum, with each peak corresponding to an optical signal wavelength and occurring at a particular time interval during the sweep. Thus, each optical signal wavelength can be associated with a particular time interval in the sweep, and, if no peak is identified during the sweep, a fault can be identified as either a laser failure or that the optical signal wavelength has drifted or 'hopped' to another optical signal wavelength. Once having identified that an optical signal has hopped, the optical source outputting that optical signal can be appropriately controlled to output light at the correct wavelength.

Wavelength and power monitor for WDM systems

Consistent with the present disclosure, clock-and-data recovery (CDR) circuitry and driver circuitry are provided on a chip that is separate from the driver circuitry, thereby reducing the amount of power consumed by the driver circuitry and simplifying system design. In one example, timing of the ERZ signals is controlled by a feedback loop that adjusts the phase of a data carrying signal relative to a clock signal, such that the phase has a desired value. Timing of the ERZ signals may thus be adjusted to minimize errors.

Electrical return-to-zero (ERZ) driver circuit

A photonic integrated circuit (PIC) chip comprising an array of modulated sources, each providing a modulated signal output at a channel wavelength different from the channel wavelength of other modulated sources and a wavelength selective combiner having an input optically coupled to received all the signal outputs from the modulated sources and provide a combined output signal on an output waveguide from the chip. The modulated sources, combiner and output waveguide are all integrated on the same chip.

Transmitter photonic integrated circuit (TxPIC) chip

An optical transmitter comprises a monolithic transmitter photonic integrated circuit (TxPIC) chip that includes an array of modulated sources formed on the PIC chip and having different operating wavelengths approximating a standardized wavelength grid and providing signal outputs of different wavelengths. A wavelength selective combiner is formed on the PIC chip having a wavelength grid passband response approximating the wavelength grid of the standardized wavelength grid. The signal outputs of the modulated sources optically coupled to inputs of the wavelength selective combiner to produce a combined signal output from the combiner. A first wavelength tuning element coupled to each of the modulated sources and a second wavelength tuning element coupled to the wavelength selective combiner. A wavelength monitoring unit is coupled to the wavelength selective combiner to sample the combined signal output. A wavelength control system coupled to the first and second wavelength tuning elements and to said wavelength monitoring unit to receive the sampled combined signal output. The wavelength control system adjusts the respective wavelengths of operation of the modulated sources to approximate or to be chirped to the standardized wavelength grid and for adjusting the optical combiner wavelength grid passband response to approximate the standardized wavelength grid.

Method of tuning optical components integrated in a monolithic photonic integrated circuit (PIC)

A transmissive active channel element is provided in each signal channel of a monolithic multi-channel TxPIC where each channel also includes a modulated source. The active channel element functions both as a power control element for both monitoring and regulating the output channel signal level of each signal channel and as a modulator for channel wavelength tagging or labeling to provide for wavelength locking the modulated sources. The power regulating function is also employed to control the channel signal power outputs of each channel to be uniform across the channel signal array. All of these functions are carried out by a feedback loop utilizing digital signal processing.

Wavelength locking and power control systems for multi-channel photonic integrated circuits (PICs)

A system, apparatus and method are described for deployment of a control loop between optical or electro-optical modules and a multiplexing module to provide a desired power profile of banded optical channel groups. The power output characteristics of the optical or electro-optical modules, the properties of the transmission paths of the banded optical channel groups, and other factors may be analyzed to allow the control loop to achieve the desired power profile on the banded optical channel groups. The control loop may adjust the output power on the optical or electro-optical modules so that the banded optical channel groups are delivered to an optical component, such as an optical multiplexer or photo-detector, having a particular optical power profile.

Active control loop for power control of optical channel groups

Growing community of inventors

Mountain View, CA, United States of America

Alan C Nilsson