T.J. Xia

Low-power high-efficiency wavelength conversion based on modulational instability in high-nonlinearity fiber

Bandwidth and peak efficiency are enhanced for wavelength conversion based on induced modulation instability by use of dispersion-shifted fiber in which the nonlinearity (n(2)/A(eff)) is enhanced by a factor of ~4.5 over that of conventional dispersion-shifted fiber. We experimentally obtain a peak conversion efficiency as high as 28 dB over a 40-nm bandwidth with 600 mW of peak pump power. Considerations for further enhancement of fiber-based wavelength conversion are also discussed.

Limitations on ultrafast optical switching in a semiconductor laser amplifier operating at transparency current

Ultrafast optical switching in a semiconductor laser amplifier (SLA) at transparency current is studied under a strong pump condition. The switch configuration is a nonlinear optical loop mirror with a SLA as the nonlinear element. We demonstrate optical switching with 2 ps recovery time and 60% nonlinear transmission at switching energy of 9 pJ. We find that the transparency current is pump power dependent and that the transparency current is different for uniform 7-bit input control pulses at 100 Gb/s. We believe these two outcomes are due to significant carrier generation via two photon absorption (TPA) at high pump intensity. To verify our hypothesis, we modify coupled propagation equations by including the carrier generation due to the TPA and solve the equations numerically. Good agreement between the experimental and simulation results is obtained. We conclude that to achieve complete pattern-independent 100 Gb/s optical switching using a SLA at transparency current, we have to avoid TPA or use the...

Demonstration and performance analysis for the off-ramp portion of an all-optical access node

Ultrafast processing of packets is demonstrated and the performance analyzed for the off-ramp portion of an all-optical access node. The off-ramp consists of synchronized fiber lasers driving an all-optical header processor that includes nonlinear optical loop mirrors (NOLM), electrooptic router, and demultiplexer in the form of a two-wavelength NOLM. We achieve switching contrasts of 10:1 for the header processor and demultiplexer with switching energies of 10 pJ and 1 pJ, respectively. Also, a proposed measurement technique to obtain eye diagrams is used to analyze the all-optical header processor using the synchronized lasers. Using this technique, we obtain an eye diagram with a Q value of 7.1/spl plusmn/0.36, which corresponds to a worst case BER value of 8.8/spl times/10/sup -12/ for a 95% confidence level. Finally, simulation models are used to verify and compare the experimental results, and we find good agreement. We also use the model to study the various causes for the degradation of the Q value through our system.

Broader and flatter supercontinuum spectra in dispersion-tailored fibers

In summary, we find experimentally that dispersion decreasing (DD) fiber produces broader and smoother supercontinuum (SC) spectra than dispersion increasing (DI) or constant dispersion fiber. At 24.3 W peak input power, the SC spectrum of DD fiber is over 100 nm wide, over twice that created by constant dispersion fiber. The spectrum is also relatively flat over the 20-nm range from 1545-1565 nm. We will also report applications of the multiwavelength SC source to erbium doped fiber amplifiers and wavelength-division multiplexed fiber characterization.

Path average measurements of optical fiber nonlinearity using solitons

This paper experimentally demonstrates a new method to determine the optical nonlinearity of single-mode optical fiber. The technique takes advantage of the well-known nonlinear response of optical fibers and well-developed models for soliton pulse propagation to extract information about the fiber characteristics. Fiber nonlinearity can degrade the performance of communication systems by, for example, causing crosstalk and signal distortions. Measuring the fiber nonlinearity would greatly aid system designers in building and upgrading communication systems. The method is utilized to determine values for n/sub 2//A/sub eff/, where n/sub 2/ is the nonlinearity of the glass and A/sub eff/ is effective area of the core. On various lengths of Corning SMF-28 fiber and Corning SMF-DS fiber. Experimentally measured propagation results for short (/spl ap/2 ps) optical pulses are compared to computer simulated models to determine the fiber nonlinearity. The method finds n/sub 2//A/sub eff/=3.0/spl times/10/sup -10/ W/sup -1/ values for short lengths (/spl ap/400 m) of Corning SMF-28 fiber and values of 2.7/spl times/10/sup -10/ W/sup -1/ for longer lengths (/spl ap/6.5 km and /spl ap/20 km). The difference is expected due to the 8/9 polarization scrambling factor, and the values are in agreement with reported literature [1]. The method also determines n/sub 2//A/sub eff/=5.6/spl times/10/sup -10/ W/sup -1/ for a /spl ap/12 km Corning dispersion shifted fiber. The method has two major regimes of operation based on the soliton period, a characteristic length for solitons. For few soliton periods (Z/Z/sub 0/ /spl sim/4) the output pulsewidth is measured as a function of launched power. The methods major advantage is its capability to measure long lengths of standard fiber, where it uses only standard diagnostic tools such as autocorrelation and optical power measurements. However, the method is only applicable in the soliton regime of fibers.

System performance measurements for an all-optical header processor using 100-Gb/s packets

We experimentally measure the eye diagram of an all-optical header processor using a crosscorrelator to achieve picosecond resolution. By varying 100-Gb/s header packets, we measure an eye diagram with a Q-value of 7.1 at 12-pJ packet pulse energy for the all-optical header processor consisting of all-optical logic gates and synchronized fiber lasers. From the Q-value, we also statistically calculate the potential bit-error-rate performance of 7.0/spl times/10/sup -13/. By measuring the change in Q-values as a function of input power, we find that input power fluctuations degrade the performance of the header processor by reducing the switching contrast of the logic gates in the header processor.

Low-power, high-efficiency wavelength conversion based on modulation instability in high nonlinearity optical fiber

Summary form only given. We have demonstrated wavelength conversion over 40 nm with a peak efficiency of 28 dB at 600-mW pump power by employing induced modulation instability in dispersion-shifted fiber with a 5 X enhancement of nonlinearity. The results are consistent with theory and show -20 dB improvement in conversion efficiency of Michelson interferometric based wavelength conversion over semiconductor-based converters.

Self-synchronization of 100-Gbit/s TDM packets using a semiconductor laser amplifier and an intensity discriminator

Using a semiconductor laser amplifier followed by an intensity discriminator, we demonstrate packet clock extraction from a 100-Gbit/s eight-bit packet where the first pulse is 20 dB higher than the remaining bits. This extracted pulse can be used to process high-speed packets with low timing jitter within each packet frame. Previous demonstrations of self-synchronization have involved marker pulses at different wavelengths, polarization, intensity, or bit period. Our scheme allows all pulses in the packet to be identical, which simplifies packet generation and propagation in high-speed TDM systems.