Roy S. Bondurant

High sensitivity optically preamplified direct detection DPSK receiver with active delay-line stabilization

The authors present experimental results for a 3 Gb/s optically preamplified, optically demodulated, differential phase shift keyed communication link achieving 62 photons/bit receiver sensitivity and using an actively stabilized optical delay line demodulator.<<ETX>>

Demonstration of return-to-zero signaling in both OOK and DPSK formats to improve receiver sensitivity in an optically preamplified receiver

Summary form only given. We demonstrate record receiver sensitivities at 1O Gb/s using RZ signaling and optimization of the optical filter bandwidths (for a Fabry-Perot optical filter and fixed 10 GHz electrical filter bandwidth). Two different modulation formats are considered: on-off keying (OOK) and differential phase shift keying (DPSK). To the best of our knowledge, this is the first demonstration of encoding phase information on RZ optical pulses to be subsequently decoded in a DPSK demodulator, and as such we christen the term RZDPSK to describe this format. Direct comparison with NRZ signaling and constant intensity DPSK reveals an improvement of about 1 dB in receiver sensitivity.

100-GHz soliton pulse train generation using soliton compression of two phase side bands from a single DFB laser

A 100-GHz soliton pulse train, with the potential of very low timing jitter, is generated using soliton compression of the beat signal between two optical carriers. The optical carriers are obtained by optically filtering out the third-order sidebands generated from a single DFB laser and a LiNbO/sub 3/ electro-optic phase modulator driven at 16.9 GHz.<<ETX>>

Overview of high-rate deep-space laser communications options

With the advent of efficient fiber laser and amplifiers, low noise photon-counting detectors, turbo-codes, and low-cost ground receiver architectures, it is now feasible to consider very high rate data links from deep space. A set of options leading to a 10-100 Mbps link from Mars to Earth is described.

LDORA: a novel laser communications receiver array architecture

We present a new laser communications receiver architecture. It consists of an array of individually mounted telescopes, each with a Geiger-mode photon counting detector array. The detector outputs are sent to a central processor using standard digital networking hardware. The concept has many benefits including low cost and scalability.

Near-quantum optimum receivers for the phase-quadrature coherent-state channel.

A theoretical analysis of two simple implementations for optical receivers that achieve near-quantum optimum performance for phase-quadrature coherent-state signaling is carried out. For a large received average photon count per symbol, N(s), the error probability is proportional to exp(-2N(s)) as opposed to the conventional heterodyne performance of exp(-N(s)/2).

Wide-field-of-view heterodyne receiver using a photorefractive double phase-conjugate mirror.

The use of a double phase-conjugate mirror to increase the angular field of view of an optical heterodyne receiver is investigated. Fields of view and overall efficiencies far larger than those predicted by the antenna theorem for conventional heterodyne systems are obtained.

Wideband frequency noise reduction and FM equalization in AlGaAs lasers using electrical feedback.

With the use of an optical frequency discriminator and negative electrical feedback, wide-bandwidth frequency noise suppression with simultaneous FM equalization of a semiconductor laser is achieved. With a heterodyne optical phase-lock loop the intermediate-frequency linewidth of two lasers, each using negative electrical feedback, was reduced from more than 25 MHz to less than 0.01 Hz.

Using fiber optics to simplify free-space lasercom systems

The use of single mode fiber optics to simplify the design of space-based optical communication systems is explored. Design considerations concerning the issues of acquisition, pointing, tracking, communication performance, efficient source-to-fiber coupling, isolation, and transmitter power limitations are presented. Preliminary experimental results of a breadboard fiber-based coherent optical communication system are also presented.

Frequency-noise cancellation in semiconductor lasers by nonlinear heterodyne detection

The bit-error-rate (BER) performance of conventional noncoherent, heterodyne frequency-shift-keyed (FSK) optical communications systems can be surpassed by the use of a differential FSK modulation format and nonlinear postdetection processing at the receiver. A BER floor exists for conventional frequency-shift keying because of the frequency noise of the transmitter and local oscillator. The use of differential frequency-shift keying with nonlinear postdetection processing suppresses this BER floor for the semiconductor laser system considered here.