S.A. Havstad

40-nm-wide tunable fiber ring laser with single-mode operation using a highly stretchable FBG

We demonstrate a 750-Hz linewidth single-mode erbium-doped fiber (EDF) ring laser with wide tunability using a widely tunable fiber Bragg grating (FBG). The stable single-mode operation is realized by using the FBG as a narrow wavelength-selective element and 4 m of unpumped EDF as a saturable absorber in the cavity. The 40-nm continuous tuning range of 1522-1562 nm is achieved using a highly stretchable FBG that exhibits a filter tuning range of over 52 nm. The grating is prepared with chemically stripped deuterium-loaded fiber to eliminate degrading factors for the grating strength, thereby achieving the wide tunability. The tuning range represents a 3.5-fold increase in wavelength tuning over previous use of FBGs.

Online chromatic dispersion monitoring and compensation using a single inband subcarrier tone

In this letter, we demonstrate a simple technique for dispersion monitoring by adding a single inband subcarrier tone to the transmitted data signal. A measurable dispersion of up to 1200 ps/nm is demonstrated in a 10-Gb/s channel using a 7-9 GHz subcarrier and the addition of the subcarrier induced a power penalty of <0.5 dB. Dynamic ranges exceeding 20 dB and resolution sensitivities better than 10 (ps/nm)/dB are shown. With an 8-GHz tone and a 15% modulation depth for 10-Gb/s signals, we show a measurement range of 975 ps/nm with a 22-dB dynamic range. We used the monitor output signal to achieve accurate tunable dispersion compensation.

Chromatic dispersion monitoring and automated compensation for NRZ and RZ data using clock regeneration and fading without adding signaling

We show that the clock signal can be extracted from both NRZ and RZ data, and that this extracted signal power represents the total accumulated dispersion. We also demonstrate dynamic dispersion compensation at 10 Gbit/s using the extracted power as a control signal.

Polarization-mode dispersion compensation in WDM systems

We demonstrate, both experimentally and numerically, polarization-mode dispersion (PMD) compensation in wavelength-division-multiplexing (WDM) systems without wavelength demultiplexing. Our technique improves the overall system performance by reducing the fading probability for the worst-performing channel at any given time. The effectiveness of our approach is based on the fact that, for moderate PMD, the probability that all channels are severely degraded at the same time is extremely small. A single-section PMD compensator reduces the 2% worst-case power penalty for a four-channel 10-Gb/s WDM system with /spl sim/42 ps average differential group delay from 9.6 to 5.3 dB.

Loop-mirror filters based on saturable-gain or -absorber gratings

We present a novel all-fiber narrow-band filter based on pump-induced saturable-gain or-absorber gratings in a loop mirror. Our design provides built-in interferometric phase alignment of the signal to the grating for optimal filtering. Notch or bandpass functionality is determined by the choice of gain or absorption and the input ports selected for the pump and signal. The loop-mirror filter has potential bandwidths from the submegahertz to beyond the gigahertz regimes, and one can tune it optically by changing the wavelength of the pump light that establishes the grating. Such filters have potential applications to wavelength-division-multiplexed optical networks and optical rf signal processing.

Tunable all-optical time-slot-interchange and wavelength conversion using difference-frequency-generation and optical buffers

In this letter, we demonstrate a module that simultaneously performs optical time-slot interchange and wavelength conversion of the bits in a 2.5-Gb/s data stream to achieve a reconfigurable time/wavelength switch. Our switch uses difference-requency-generation (DFG) for wavelength conversion and fiber Bragg gratings as wavelength-dependent optical time buffers. This tunable technique employs high-extinction-ratio and low-additive-noise DFG.

Monitoring chromatic dispersion and PMD impairments in optical differential phaseshift-keyed (DPSK) systems

We simulate and measure chromatic dispersion and polarization mode dispersion impairments, and demonstrate their monitoring by measuring clock tone power and degree of polarization in DPSK and RZ-DPSK systems.

Dispersion monitoring and compensation using a single inband subcarrier tone

We demonstrate a simple technique for dispersion monitoring by adding a single inband tone to the data. Our technique has high accuracy and an easily reconfigurable measurement range. Dispersion compensation is also demonstrated using the monitors output.

Distance-independent microwave and millimeter-wave power fading compensation using a phase diversity configuration

We use a nonlinearly chirped fiber Bragg grating in a phase diversity configuration to achieve distance-independent microwave and millimeter-wave dispersion-induced power fading compensation for double-sideband subcarrier-multiplexed systems. We demonstrate compensation for power fading over 150 km at 8 and 12 GHz, with received subcarrier power in all cases uniform to within 1 dB.

All-optical output-port contention resolution using subcarrier-multiplexing

We demonstrate an all-optical contention resolution technique that preserves the wavelength of two same-wavelength contending incoming 2.5 Gbit/s channels. This is achieved by optically subcarrier-multiplexing one channel to a higher RF frequency beyond the first baseband channel on the same input wavelength. By using narrow (/spl sim/5 GHz) fiber Fabry-Perot filters for demultiplexing we recovered each channel using a baseband receiver with <1 dB power penalty.