Wavelength conversion using fiber cross-phase modulation driven by two pump waves.

Wavelength conversion using all-optical phase modulation in a fiber driven by two pump waves is investigated. The operation features are analyzed using an all-optical phase modulation model with two parallel-/cross-polarized pump waves to generate a phase-preserving copy of the optical signal at an exact frequency up-/down-shifted by the two-pump detuning. The conversion efficiency is experimentally verified using a 300-m highly-nonlinear fiber. The results agree well with a theoretical prediction. The conversion bandwidth over 4 THz is achieved and error-free wavelength conversion for a 32-GBd polarization-division multiplexed 16QAM signal is demonstrated. The technique's applicability to a large-capacity wavelength-division multiplexed signals is also discussed.

Experimental Investigation of 126-Gb/s 6PolSK-QPSK signals.

We experimentally generate 28-GBd 6-ary polarization-shift keying quadrature phase-shift keying (6PolSK-QPSK) signals by utilizing a high-speed 4-channel digital-to-analog converter and an integrated dual-polarization I/Q modulator. In WDM transmission experiments over up to 4800 km standard single-mode fiber, we compare the performance of 126-Gb/s 6PolSK-QPSK and 112-Gb/s polarization-division multiplexing (PDM) QPSK signals. Furthermore, we discuss the implications of applying an inner Reed-Solomon RS(511,455) forward error correction code in order to correct burst errors due to the anti-Gray mapping of 6PolSK-QPSK.

Experimental demonstration of a format-flexible single-carrier coherent receiver using data-aided digital signal processing.

We experimentally demonstrate the use of data-aided digital signal processing for format-flexible coherent reception of different 28-GBd PDM and 4D modulated signals in WDM transmission experiments over up to 7680 km SSMF by using the same resource-efficient digital signal processing algorithms for the equalization of all formats. Stable and regular performance in the nonlinear transmission regime is confirmed.

A self-coherent receiver for detection of PolMUX coherent signals.

A self-coherent receiver capable of demultiplexing PolMUX-signals without an external polarization controller is presented. Training sequences are introduced to estimate the polarization rotation, and a decision feedback recursive algorithm mitigates the random walk of the recovered field. The concept is tested for a PolMUX-DQPSK modulation format where one polarization carries a normal DQPSK signal while the other polarization is encoded as a progressive phase-shift DQPSK signal. An experimental demonstration of the scheme for a 112 Gbit/s PolMUX-DQPSK signal is presented.

40 Gb/s wavelength conversion via four-wave mixing in a quantum-dot semiconductor optical amplifier.

The static and dynamic characteristics of degenerate four-wave mixing in a quantum dot semiconductor optical amplifier are investigated. A high chip conversion efficiency of 1.5 dB at 0.3 nm detuning, a low (< 5 dB) asymmetry of up and down conversion and a spectral conversion range of 15 nm with an optical signal-to-noise ratio above 20 dB is observed. The comparison of pumping near the gain peak and at the edge of the gain spectrum reveals the optical signal-to-noise ratio as the crucial parameter for error-free wavelength conversion. Small-signal bandwidths well beyond 40 GHz and 40 Gb/s error-free 5 nm wavelength down conversion with penalties below 1 dB are presented. Due to the optical signal-to-noise ratio limitation, wavelength up conversion is error-free at a pump wavelength of 1311 nm with a penalty of 2.5 dB, whereas an error floor is observed for pumping at 1291 nm. A dual pump configuration is demonstrated, to extend the wavelength conversion range enabling 15.4 nm error-free wavelength up conversion with 3.5 dB penalty caused by the additional saturation of the second pump. This is the first time that 40 Gb/s error-free wavelength conversion via four-wave mixing in quantum-dot semiconductor optical amplifiers is presented.

Comparison of 8 × 112 Gb/s PS-QPSK and PDM-QPSK signals over transoceanic distances.

We experimentally investigate polarization-switched quadrature phase-shift keying (PS-QPSK) with a symbol rate of 37.3 GBd corresponding to a bit rate of 112 Gb/s. In a wavelength-division multiplexing (WDM) experiment with 50 GHz channel spacing, the transmission performance of PS-QPSK is compared to that of polarization-division multiplexed QPSK (PDM-QPSK) over an EDFA amplified ultra-large-effective-area fiber link. For a bit-error ratio (BER) of 3.8 × 10(-3), the achieved transmission distance is 11000 km for PS-QSPK and 10000 km for PDM-QPSK.

Experimental investigation of 84-Gb/s and 112-Gb/s polarization-switched quadrature phase-shift keying signals.

We experimentally investigate 28-GBd (84-Gb/s) and 37.3-GBd (112-Gb/s) polarization-switched quadrature phase-shift keying (PS-QPSK) signals. In single-channel transmission experiments over up to 12500 km ultra large effective area fiber, we compare their performance to that of polarization-division multiplexing quadrature phase-shift keying (PDM-QPSK) signals at the same bit rates. The experimental results show that PS-QPSK not only benefits from its better sensitivity but also offers an increased tolerance to intra-channel nonlinearities.

80 Gb/s wavelength conversion using a quantum-dot semiconductor optical amplifier and optical filtering.

Wavelength conversion of 40 Gb/s and 80 Gb/s return-to-zero on-off-keying signals using a quantum-dot semiconductor optical amplifier in combination with a delay interferometer as subsequent filter is demonstrated. The performance of the 80 Gb/s wavelength converter measured in terms of the bit-error ratio demonstrated here is the highest reported up to now for quantum-dot semiconductor optical amplifiers. The typical fast gain dynamics manifests itself in open eye diagrams of the converted signal. The slow phase dynamics of the carrier reservoir however induces severe patterning and requires compensation. Adaptation of the free-spectral range of the delay interferometer is necessary in order to mitigate these phase effects and to achieve error-free wavelength conversion.

110 km transmission of 160 Gbit/s RZ-DQPSK signals by midspan polarization-insensitive optical phase conjugation in a Ti:PPLN waveguide.

We demonstrate 160 Gbit/s return-to-zero (RZ) differential quarternary phase-shift keying (DQPSK) signal transmission over a 110 km single-mode fiber by taking advantage of mid-span optical phase conjugation (OPC). The technique is based on nonlinear wavelength conversion by cascaded second harmonic and difference frequency generation in a Ti:PPLN waveguide. Error-free operation with a negligible optical signal-to-noise ratio penalty for the signal after the OPC transmission without and with polarization scrambling was achieved. The results also show the polarization insensitivity of the OPC system using a polarization diversity scheme.