D. Mahgerefteh

Effect of first-order PMD compensation on the statistics of pulse broadening in a fiber with randomly varying birefringence

Polarization mode dispersion in standard telecommunication fibers can be compensated to first order by using the concept of principal states of polarization. At the receiver the pulse is decomposed into the two waveforms polarized along the two principal states for the optical link and their delay is removed. We show by Monte Carlo simulation that compensation sharpens the probability distribution function of the pulse durations by a factor that decreases with increasing polarization dispersion.

Technique for measurement of the Raman gain coefficient in optical fibers

We demonstrate a simple, novel technique for measurement of the Raman gain spectrum in optical fibers. We measure the stimulated Raman scattered power generated by a square pulse as a function of its pulse width. Because of fiber dispersion, increasing the pulse width increases the interaction length of the pump and Stokes pulses and leads to a higher Stokes power. The dependence of growth rate of Stokes power on pulse width gives the Raman gain coefficient. Our technique does not require calibration against a standard or absolute measurement of the Stokes signal. We show that gain values obtained with this technique agree well with direct pump-probe measurements.

CARRIER TRANSPORT IN A PHOTOREFRACTIVE MULTIPLE QUANTUM WELL DEVICE

Using picosecond time‐resolved four‐wave mixing we have investigated the turn‐on and turn‐off mechanisms in a photorefractive multiple quantum well spatial light modulator with Stark geometry. We show that holes contribute to the turn‐on time as a slower rise (∼300 ps) of the diffraction efficiency. Furthermore, the diffraction grating is dominated by either electrons or holes, depending on the applied voltage polarity relative to the diffraction of illumination. The grating decays in 0.4–8.5 ns, depending on the grating spacing. We show that the decay is due to lateral transport of carriers at the multiple quantum well/dielectric interfaces, where low‐temperature grown layers can increase the diffraction efficiency and device resolution.

All-optical 1.5 μm to 1.3 μm wavelength conversion in a walk-off compensating nonlinear optical loop mirror

We demonstrate highly efficient all-optical conversion from 1.5 /spl mu/m to 1.3 /spl mu/m using a novel nonlinear optical loop mirror that compensates for walk-off. We make the fiber loop by splicing alternating segments of standard single-mode and dispersion-shifted fibers and choose their lengths such that the walk-off of the 1.3 /spl mu/m and 1.5 /spl mu/m pulses in one segment is completely reversed in the adjacent segment. We also show that the width of the converted pulses can be tailored by this scheme.<<ETX>>

10 Gb/s RZ to NRZ format conversion using a semiconductor-optical-amplifier/fiber-Bragg-grating wavelength converter

We report operation of a non-interferometric semiconductor-optical-amplifier/fiber-Bragg hybrid device for simultaneous RZ to NRZ data format and wavelength conversion. Error-free conversion to non-inverted NRZ data is achieved at 10 Gb/s.

Effect of randomly varying birefringence on the Raman gain in optical fibers

**BT Laboratories, Martlesham Heath, Ipswich IP5 7RE, United Kingdom 1. D. A. Nolan, W. J. Miller, in Optical Fiber Communication Conference Vol. 4, OSA 1994 Technical Digest Series (OSA, Washington DC), 94-95. T. Morika, H. Takara, S. Kawanish, T. Kitoh, M. Saruwatari, Electron. Lett. 32, 833 (1996). I. Glesk, J. P. Sokoloff, P. R. Prucnal, Electron. Lett. 30,33 (1994). M. Jiang, W. Sha, L. Rahman, B. C. Barnett, J. K. Andersen, M. N. Islam, K. V. Reddy, Opt. Lett. 21,809 (1996). 2.

Improved transmission of chirped signals from semiconductor optical devices by pulse reshaping using a fiber Bragg grating filter

Spectral filtering of chirped signals with an edge of a fiber grating filter improves propagation in nondispersion-shifted fiber. The improvement is due to a temporal shift of the frequency modulation with respect to the amplitude modulation. By filtering the chirped output of a semiconductor optical amplifier (SOA) wavelength converter with a fiber grating edge we obtain error-free transmission of converted data through 100 km of nondispersion-shifted fiber at 5 Gb/s.

Wavelength-stabilized source of nearly transform limited optical pulses for 10 Gb/s RZ transmission

Summary form only given. The RZ format is being considered for us in 10 Gb/s transoceanic transmission systems, requiring inexpensive, compact, and jitter-free optical pulses. The authors introduce a direct laser modulation 1551 nm DFB laser at 81.8 mA, modulated with 6.5 dBm of RF power at 9.953 GHz, producing a phase modulated signal with a small 44% intensity modulation.

Improved frequency response of a semiconductor-optical-amplifier wavelength converter using a fiber Bragg grating

We demonstrated a novel SOA-fiber-grating wavelength converter for RZ data that has a better frequency response than a single SOA wavelength converter at the same optical power level. The SOA-fiber-grating wavelength converter uses a single amplifier and requires no interferometers. The principle of this device is described as follows: Consider an input pump beam at /spl lambda//sub 1/ and a CW probing signal at /spl lambda//sub 2/ coincident in the amplifier. The pump beam partially depletes the gain of the amplifier. This rapidly increases the refractive index of the semiconductor and chirps the CW signal at /spl lambda//sub 1/ towards the red, There is a smaller, blue chirp associated with the slower recovery of the amplifiers gain. The probing signals wavelength, /spl lambda//sub 2/, is adjusted such that the fiber grating passes the red chirped portion of the CW signal and blocks its unchanged spectral components. We use a more compact, fiber grating step filter than previous devices which selects the phase modulated portions of the probing signal more effectively.

All-optical 2R-regeneration of 10 Gbit/s RZ data transmitted over 30000 km in a dispersion-managed system using an electroabsorption modulator

All-optical 2R regeneration of 10 Gbit/s RZ data transmitted over 30000 km in a dispersion-managed system was demonstrated using an electroabsorption modulator at the receiver. The modulator suppresses the accumulated optical noise, improving the signal-to-noise ratio of the transmitted data.