J.E. Johnson

Predistortion of electroabsorption modulators for analog CATV systems at 1.55 /spl mu/m

A predistortion circuit with adjustable amounts of third- and fifth-order predistortion is studied both theoretically and experimentally. The circuit is used to cancel the third- and fifth-order intermodulation distortion of a 1.55-/spl mu/m integrated electroabsorption modulator/DFB laser. The CSO obtained is -61 dBc and the CTB is reduced 22.6 dB to -65 dBc. This performance is maintained after fiber amplification and propagation through 13 km of nondispersion shifted fiber due to the modulators low chirp. Dithering of the DFB lasers injection current is employed to increase the stimulated Brillouin scattering (SBS) threshold to +13.4 dBm.

Optoelectronic phase-locked loop with balanced photodetection for clock recovery in high-speed optical time-division-multiplexed systems

An optoelectronic phase-locked loop (PLL) for clock recovery in high-speed optical time-division-multiplexed (OTDM) systems is proposed and experimentally demonstrated. The proposed scheme incorporates a pair of balanced photodetector through which the polarity ambiguity in error signal is resolved, and the cancellation of laser noise enables clock recovery with low timing jitter. Using an electroabsorption modulator as a phase detector, a 10-GHz clock signal with root-mean-square (rms) timing jitter of 300 fs is successfully extracted from 40 and 80 Gb/s return-to-zero (RZ) data stream. A 40- to 10-Gb/s demultiplexing is performed by using the recovered clock signal with no penalty introduced in the bit error rate performance.

Dispersion-penalty-free transmission over 130-km standard fiber using a 1.55-μm, 10-Gb/s integrated EA/DFB laser with low-extinction ratio and negative chirp

Transmission performance of a 10-Gb/s integrated electroabsorption modulator/DFB laser has been evaluated in terms of the eye margin degradation and the receiver sensitivity penalty caused by the chromatic dispersion in the standard (non-DSF) fiber. Combination of low extinction ratio (/spl epsi/=5 dB) and negative chirp (/spl Delta/v=-0.01 nm) operation allows 10-Gb/s transmission over 130-km standard fiber without any dispersion penalty in receiver sensitivity (for 10/sup -9/ BER) and with a 7% eye margin for 10/sup -15/ BER.

320 Gbit/s single-channel pseudo-linear transmission over 200 km of nonzero-dispersion fiber

Single-channel transmission at 320 Gbit/s is demonstrated over record length of 200 km (2/spl times/100 km) of nonzero-dispersion fiber. Semiconductor based transmitter, demultiplexer and clock recovery is employed as well as uncorrelated multiplexing in the transmitter.

Linearization of 1.55-/spl mu/m electroabsorption modulated laser by distortion emulation and reversal for 77-channel CATV transmission

An electroabsorption modulated laser (EML) is linearized by emulation and reversal of the nonlinear distortion using a companion EML inside an optoelectronic interferometer. Suppression of composite second-order and triple-beat signals to <-61 and <-63 dBc, respectively, have been achieved for a carrier-to-noise ratio (CNR) of 50 dB with a 77-channel loading of CATV carriers. Further performance enhancement can be expected through tailoring of device and component characteristics to suit the application.

Assessment and modeling of aging in electro-absorption distributed Bragg reflector lasers

We describe a protocol for assessing aging in the tuning section of a multisection distributed Bragg reflector laser integrated with amplifier, tap coupler, and electro-absorption modulator. Under accelerated aging, we observe a transient change of nonradiative recombination followed by saturation. A simple model of aging of the Bragg section of the tunable lasers enables prediction of changes in each wavelength channel using information obtained from a single channel only.

Nonlinear servo control of MEMS mirrors and their performance in a large port-count optical switch

In this paper, we demonstrate full closed-loop control of electrostatically actuated double-gimbaled MEMS mirrors and use them in an optical cross-connect. We show switching times of less than 10 ms and optical power stability of better than 0.2 dB. The mirrors, made from 10-/spl mu/m-thick single-crystal silicon and with a radius of 400-450 /spl mu/m, are able to tilt to 8/spl deg/ corresponding to 80% of touchdown angle. This is achieved using a nonlinear closed-loop control algorithm, which also results in a maximum actuation voltage of 85 V, and a pointing accuracy of less than 150 /spl mu/rad. This paper will describe the MEMS mirror and actuator design, modeling, servo design, and measurement results.We demonstrate full closed-loop control of electrostatically actuated double-gimbaled MEMS mirrors and use them in a free space optical cross-connect with switching times of less than 10 ms, and optical power stability of better than 0.2 dB.

2.5 Gb/s transmission over 680 km using a fully stabilized 20 channel DBR laser with monolithically integrated semiconductor optical amplifier, photodetector and electroabsorption modulator

We demonstrate for the first time a fully functional 2.5 Gb/s EA-modulated wavelength-selectable laser module meeting all long-haul transmission requirements for stability, chirp, power and linewidth over 20 channels on a 50 GHz grid. Based on a highly integrated InP chip comprising a DBR laser, semiconductor optical amplifier, power monitor, and EA-modulator, the module also contains optics to ensure simultaneous long-term wavelength and mode stability.

Experimental demonstration of composite packet switching on a WDM photonic slot routing network

We propose photonic slot routing ring networks that use a novel packet stacking technique to add/drop packets, which are simultaneously time and wavelength division multiplexed. Packet stacking, routing, and unstacking with four wavelengths was successfully demonstrated.

High-speed integrated electroabsorption modulators

The explosive growth in internet, multimedia and wireless traffic in recent years is rapidly exhausting capacity in public networks worldwide, forcing network service providers to aggressively install new lines and upgrade old ones. Fortunately, technological breakthroughs in the areas of erbium-doped fiber amplifiers (EDFAs), passive wavelength demultiplexers and low chirp sources have made all-optical dense wavelength-division multiplexed (WDM) systems a cost- effective way to utilize the vast bandwidth already available in the embedded fiber plant. WDM systems offer additional operational advantages, including high ultimate capacity, bit-rate transparency, flexible growth strategies, and the potential to use all-optical wavelength routing in future broadband network architectures. Commercial WDM systems operating at the OC-48 (2.5 Gbit/s) line rate are now available, and OC-192 (10 Gbit/s) terminal equipment which is under development will further enhance the capacity of these systems. One of the keys to viable WDM systems is the availability of inexpensive low-chirp optical transmitters. By taking advantage of photonic integrated circuit technology, it is possible to produce monolithically integrated DFB laser/EA modulators (EMLs) with low chirp, low drive voltage and high extinction ratio, in a single compact package. In this talk we discuss the operating characteristics of these devices and their relationship to WDM system performance.