L.-S. Yan

High-speed electrooptic modulator characterization using optical spectrum analysis

This paper presents our latest studies on high-speed electrooptic modulator characterization using the optical spectrum analysis method. Several new characterization techniques are theoretically analyzed and experimentally demonstrated for the measurement of critical device parameters at very high modulation frequencies. Applying this method in our wide-band electrooptic (EO) modulator characterization experiment, we have successfully measured halfwave voltages, frequency responses, and the chirp parameter at frequencies over 10 GHz for several typical high-speed LiNbO/sub 3/ modulators. Our experiment showed that the optical spectrum analysis provides an accurate and convenient platform for ultra-high-speed EO modulator characterization.

Chromatic dispersion monitoring technique using sideband optical filtering and clock phase-shift detection

We propose and demonstrate a novel technique for 40- and 10-Gb/s chromatic dispersion monitoring that uses an optical filter to select the upper and lower vestigial-sideband (VSB) signals in the transmitted optical data and determine the relative clock phase shift caused by dispersion. Without modification of transmitters, this technique provides low cost chromatic dispersion monitoring for WDM systems, <3 ps/nm dispersion resolution for 40-Gb/s data, and greatly reduced sensitivity to the influence of polarization mode dispersion.

Monitoring and control of polarization-related impairments in optical fiber systems

Polarization-related impairments have become a critical issue for high-data-rate optical systems, particularly when considering polarization-mode dispersion (PMD) and polarization-dependent loss (PDL). In general, polarization effects are stochastic processes and can occur on short or long time scales. Therefore, control and monitoring of these effects may be crucial in any systems-level mitigation. This tutorial will highlight the following key issues: PMD and PDL, monitoring schemes, emulation of proper statistics, interaction, and applications of polarization scrambling.

Optical Signal Processing Using Tunable Delay Elements Based on Slow Light

Tunable optical delay lines have many applications for high-performance optical switching and signal processing. Slow light has emerged as an enabling technology for achieving continuously tunable optical delays. Delay reconfigurability opens up a whole new field of nonlinear signal processing using slow light. In this paper, the authors review recent advances in slow-light-based optical signal processing, with a focus on the data fidelity after traversing the slow light elements. The concept of slow-light-induced data pattern dependence is introduced and is shown to be the main signal degrading effect. We then propose and experimentally demonstrate phase-preserving slow light by delaying 10 Gb/s differential phase-shift keying (DPSK) signals with reduced DPSK pattern dependence. Spectrally efficient slow light using advanced multilevel phase-modulated formats is further described. With this technique, doubled bit-rate signals can be transmitted through a bandwidth-limited slow light element. We finally show several novel slow-light-based signal processing modules. Unique features such as multichannel operation, variable bit-rate capability, and simultaneous multiple functions are highlighted.

Tunable all-optical wavelength conversion and wavelength multicasting using orthogonally polarized fiber FWM

All-optical wavelength conversion and multicasting with input and output wavelength tunability is a desired component for reconfigurable wavelength-division-multiplexed (WDM) networks for improving the efficiency and performance. In this paper, we propose a novel tunable all-optical wavelength-conversion-and-wavelength-multicasting schemes by using orthogonally polarized nondegenerate four-wave mixing (FWM) in highly nonlinear fiber. The input signal is amplified and serves as one of the two pumps. Wide tunability is obtained by placing a dummy pump and dummy signals at appropriate wavelengths with respect to the input wavelength and desired output wavelengths. For a 10-Gb/s NRZ system, 1:3 multicasting is demonstrated with a less than 0.6-dB power penalty, over a 25-nm tuning range for both input and output signals.

44-ns Continuously Tunable Dispersionless Optical Delay Element Using a PPLN Waveguide With Two-Pump Configuration, DCF, and a Dispersion Compensator

This letter presents an optically controlled, continuously tunable, dispersionless optical delay element in fiber based on a selective wavelength converter using a periodically poled lithium-niobate waveguide with two-pump configuration, dispersion-compensated fiber, and a dispersion compensator. Optical phase information is preserved in this technique, and there is no fundamental limitation on pulsewidth or bit rate. A Continuous optical delay up to 44-ns is shown for 10-Gb/s nonreturn-to-zero applications, which is equal to a 440-bit slot

Programmable group-delay module using binary polarization switching

We demonstrate the first programmable group-delay module based on polarization switching. With a unique binary tuning mechanism, the device can generate any differential group delay value from -45 to +45 ps with a resolution of 1.40 ps, or any true-time-delay value from 0 to 45 ps with a resolution of 0.7 ps. The delay varying speeds for both applications are under 1 ms and can be as fast as 0.1 ms. We evaluate both the dynamic and static performances of the device while paying special attention to its dynamic figures of merit for polarization-mode dispersion emulation and compensation applications. Our experiment shows that the device exhibits a negligible transient-effect induced power penalty (<0.2 dB) in a 10-Gb/s nonreturn-to-zero system.

Slow light on Gbit/s differential-phase-shift-keying signals

We demonstrate, via simulation and experiment, slowing down of a phase-modulated optical signal. A 10.7-Gb/s NRZ-DPSK signal can be delayed by as much as 42 ps while still achieving error free via broadband SBS-based slow light. We further analyze the impact of slow-light-induced data-pattern dependence on both constructive and destructive demodulated ports. By detuning the SBS gain profile, we achieve 3-dB Q-factor improvement by the reduction of pattern dependence. Performance comparison between NRZ-DPSK and RZ-DPSK shows that robustness to slow-light-induced pattern dependence is modulation format dependent.

All-optical XOR gate using polarization rotation in single highly nonlinear fiber

We demonstrate a 10-Gb/s all-optical XOR gate based on polarization rotation induced by Kerr effect in a single highly nonlinear fiber (HNLF). Using 2 km of HNLF with a nonlinear coefficient of 9.1 W/sup -1//spl middot/km/sup -1/, we obtain a 25-dB extinction ratio at the XOR output.

Width-tunable optical RZ pulse train generation based on four-wave mixing in highly nonlinear fiber

We demonstrate a simple technique for width-tunable optical return-to-zero pulse train generation based on four-wave mixing in highly nonlinear fiber. By electrically tuning the delay between two pump pulse trains, the pulsewidth of a generated pulse train is continuously tuned. In our experiment, the full-width at half-maximum (FWHM) of a 5G pulse train is tuned from 85 to 25 ps, and the FWHM of a 10G pulse train is tuned from 33 to 18 ps. And the simulation results show that the FWHM of a 40G pulse train can be tuned continuously from 10.6 to 2.9 ps. Negligible power penalty is observed after 59-km single-mode fiber and 11.4-km dispersion-compensation-fiber transmission for different pulsewidths at 10 Gb/s.