Bamdad Bakhshi

Direct generation of subpicosecond chirp-free pulses at 10 GHz from a nonpolarization maintaining actively mode-locked fiber ring laser

0.7-1.3 ps highly stable, transform-limited, sech/sup 2/-shaped pulses at 10 GHz in the 1536-1569 nm wavelength region from a nonpolarization maintaining (PM), single intensity modulator, actively and harmonically mode-locked fiber ring laser have been directly generated. Little degradation of long-term stability of the laser operation was observed due to the non-PM nature of the laser cavity.

First dispersion-flattened transpacific undersea system: from design to terabit/s field trial

The 8991-km-long transpacific segment of the Tyco Global Network (TGN) [TGN is a trademark of Tyco Telecommunications, Eatontown, NJ 07724 USA], connecting Hillsboro, Oregon, USA to Toyohashi, Japan, is the first installed dispersion-flattened dense wavelength division multiplexed (DWDM) system. In this paper, we describe the development path bringing this system from the computer design stage to a field trial, which confirms that the installed segment can support the design capacity of 96/spl times/10 Gb/s customer channels per fiber pair. Commercial channels have been provisioned on this segment with satisfactory system margins. Exploratory transmission results at 128/spl times/12.3 Gb/s over this segment are also reported here. The experimental results agree well with our expectations based on the results from our system design simulator.

Dual-wavelength 10-GHz actively mode-locked erbium fiber laser

We present the first 10 GHz dual-wavelength actively mode-locked erbium fiber laser (ML-EFL). Dual-wavelength operation is achieved by introducing two intracavity branches, each containing a tunable optical bandpass filter. A variable output coupler combining the filter branches also equalizes the effective cavity gain for the two wavelengths, By adjusting the filters and the coupler, dual-wavelength ML-EFL operation is achieved at different wavelengths. Nearly transform-limited, 4- and 6.2-ps-wide 10-GHz soliton pulses are e.g., simultaneously generated at 1542.3 and 1563.8 nm, respectively. The experimental results agree very well with analytical calculations.

Soliton interaction penalty reduction by receiver filtering

We present the first detailed numerical study of the impact of receiver low-pass filtering in soliton interaction-limited communication systems. We propagate 40-Gb/s pseudorandom bit sequences (PRBSs) of 2/sup 8/-1 solitons up to one soliton collision distance (z/sub c/) and optimize the filter bandwidth to minimize the interaction induced eye opening penalty. The distance at 0.5-dB penalty is increased over 40% through filtering. The penalty is essentially pulsewidth independent when considering distances normalized by z/sub c/. We also show that PRBSs of at least 2/sup 8/-1 solitons are required to accurately simulate random data.

Using RZ DPSK-Based Transponders for Upgrades on Existing Long-Haul Submarine WDM Systems

The RZ-DPSK transmission format allows higher capacity and greater flexibility in system configurations when upgrading existing WDM systems. We report on using RZ-DPSK for upgrades of systems originally designed for RZ-OOK transponders. In this paper, we discuss the use of RZ-DPSK transponders on an installed trans-Pacific link and on the Sam-1 Cable System where the original transmission lengths were significantly increased. On the original Sam-1 Cable System, each digital line segment was less than 5000 km long. At the owners request these shorter sections were concatenated to make a 10,757-km commercial WDM 10 Gb/s fiber optic link, the longest in the world. Ten Gb/s transponders were successfully deployed onto the concatenated segments, and DPSK transponders will allow 480 Gb/s capacity.

Measurement of the differential group delay in installed optical fibers using polarization multiplexed solitons

We experimentally demonstrate a new technique for measurement of the differential group delay (DGD) in optical fibers using polarization-division multiplexed (PDM) solitons: the change in the separation of orthogonally polarized solitons propagating along different principal axes in a fiber equals the DGD at the signal wavelength. Based on this principle, we use PDM solitons to measure the accumulated DGD at different distances along a 400-km installed fiber. The measured DGD exhibits the expected square-root-of-length dependence, corresponding to a polarization-mode dispersion of 0.26 ps/km/sup 1/2/. The results are in excellent agreement with those obtained by a commercial instrument utilizing Jones matrix eigenanalysis.

Transmission of 8×40 Gb/s RZ-DQPSK Signals Over a 401 km Unrepeatered Link

We successfully transmitted 8x40 Gb/s RZ-DQPSK channels over a 401 km unrepeatered link with 68 dB loss. This was enabled by low loss fiber, high power booster amplifier, and ROPA technology. All channels had >13.5 dB Q-factor after transmission.

Coherent friendly dispersion Map for direct detection transmission formats

A dispersion map that meets the conflicting needs of coherent and direct detection transmission is presented. Performance improvements over a conventional map are verified for coherent transmission by experiments and simulations.

Light-Capacity Loading Studies Over an Installed 28-nm Standard Dispersion-Map Transpacific WDM System

We present the first detailed study of lightly loaded long-haul WDM systems. We examine how channel performance depends on wavelength and power allocation of idlers in a lightly loaded 28-nm installed transpacific system.

An experimental analysis of performance fluctuations in high-capacity repeaterless WDM Systems

We present an investigation of performance fluctuations in high-capacity repeaterless WDM systems. In a 32/spl times/12.3 Gb/s 410 km transmission experiment, nonlinear channel cross-talk causes > 1.5 dB Q-factor fluctuation. System design must include sufficient margin for these fluctuations.