Multichannel frequency conversion experiment using fibre four-wave mixing

Multichannel frequency conversion is demonstrated using four-wave mixing. A polarisation independent configuration is employed, by which polarisation control for each signal is not necessary. By setting the pump light frequency at the zero-dispersion wavelength of the fibre, three FSK modulated signals with a frequency spacing of 70 GHz are simultaneously converted with an equal efficiency of -27.5 dB. Bit error rate measurements confirm the feasibility of this conversion scheme.<>     

Picosecond optical sampling using four-wave mixing in fibre

An all-optical sampling system with 20 ps resolution realised by employing four-wave mixing in a fibre is demonstrated. Using only semiconductor laser sources, picosecond pulses are displayed on a microsecond time scale with a low speed receiver.<>     

Wavelength conversion up to 18 nm at 10 Gb/s by four-wave mixing in a semiconductor optical amplifier

We characterize the conversion bandwidth of a four-wave mixing semiconductor optical amplifier wavelength converter. Conversion of 10-Gb/s signals with bit-error-rate (BER) performance of <10/sup -9/ is demonstrated for wavelength down-shifts of up to 18 nm and upshifts of up to 10 nm.     

Theoretical analysis of polarisation-insensitive wavelength conversion by four-wave mixing in photonic crystal fibre

Polarisation-insensitive wavelength conversion by four-wave mixing (FWM) has been demonstrated in a 20 m short nonlinear photonics crystal fibre. Theoretical analysis confirms that the combination of a 45deg pump launch and a minimum pump-probe detuning is required to reduce the polarisation sensitivity of FWM to ~1 dB.     

320/640 GHz high-quality pulse sources based on multiple four-wave mixing in highly nonlinear optical fibre

Ultra-high repetition rate quality pulse trains have been generated in a highly nonlinear optical fibre through the compression of a dual-frequency beat-signal based on a multiple four-wave mixing process. FROG analyses show that 500 and 300 fs transform-limited pulses have been generated at 320 and 640 GHz, respectively, over a 20 nm wavelength range.     

Wavelength conversion at 10 Gb/s by four-wave mixing over a 30-nminterval

We show that the use of a long semiconductor optical amplifier increases the error-free conversion interval of a four-wave mixing (FWM)-based wavelength converter. 30-nm wavelength down-conversion and 15-nm up-conversion have been obtained at 10 Gb/s. This result is a significant improvement over the previous best performance of a FWM-based wavelength converter and suggests that the full erbium-doped fiber amplifier bandwidth can be covered with FWM wavelength converters     

Wavelength conversion by four-wave mixing in semiconductor opticalamplifiers

Time-resolved spectral analysis is performed on 10 Gb/s signals wavelength converted by four-wave mixing (FWM) in semiconductor optical amplifiers. A pattern-dependent chirp resulting from parasitic gain modulation by the signal is measured and characterized as a function of the converter's pump-to-probe ratio. This chirp is found to be insignificant for pump-to-probe ratios exceeding 9 dB     

Widely tunable four-wave mixing in semiconductor optical amplifierswith constant conversion efficiency

The conversion efficiency and output signal-to-noise ratio (SNR) of single-pump four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is strongly dependent on frequency shift. We examine a scheme for FWM in SOAs that uses two orthogonally polarized pumps. We compare experimentally and theoretically the conversion efficiency and SNR of the orthogonal-pump scheme with single-pump FWM. The orthogonal-pump scheme has nearly constant conversion efficiency and SNR over the 4.5-THz range of frequency shifts measured. Experimental and theoretical results for the conversion efficiency and SNR of the orthogonal-pump scheme agree to within 3.5 dB     

Theory of four-wave mixing wavelength conversion in quantum dot semiconductor optical amplifiers

Detailed theoretical analysis of four-wave mixing (FWM) wavelength conversion in quantum dot semiconductor optical amplifier (QD-SOA) is presented. The model takes into account the effect of the multidiscrete QD energy levels and the wetting layer. Good agreement between calculated and experimental data is obtained. Because of the discreteness of the energy levels, QD-SOAs demonstrate high FWM conversion efficiencies at high detuning frequency. Our calculations show that carrier escape from the ground state significantly affects the performance of the amplifier.     

Effect of fibre dispersion on four-wave mixing in multichannel coherent optical transmission system

Severe bit error rate degradations and strong error rate floors caused by fibre four-wave mixing (FWM) in a high launch power, seven channel, coherent optical transmission system are reported. The critical influence of fibre chronic dispersion is highlighted, with a negligible penalty after transmission over conventional step index fibre, even for a launch power of +17 dBm. Several orders of FWM products are visible in the optical spectra for dispersion shifted fibre.<>     

Cascaded wavelength conversion by four-wave mixing in a strained semiconductor optical amplifier at 10 Gb/s

We demonstrate for the first time cascaded wavelength conversion by four-wave mixing in a semiconductor optical amplifier. Bit-error-rate performance of <10/sup -9/ at 10 Gb/s is achieved for two conversions of up to 9 nm down and up in wavelength. For two wavelength conversions of 5 nm down and up, a power penalty of 1.3 dB is measured. A system of two wavelength converters spanning 40 km of single-mode fiber is also demonstrated.     

Broad-band wavelength conversion based on cross-gain modulation and four-wave mixing in InAs-InP quantum-dash semiconductor optical amplifiers operating at 1550 nm

Wavelength conversion based on four-wave mixing (FWM) and cross-gain modulation (XGM) is experimentally demonstrated for the first time in a 1550-nm InAs-InP quantum-dash semiconductor optical amplifier. Continuous-wave FWM with a symmetric conversion efficiency dependence on detuning direction and FWM mediated short-pulse wavelength conversion are demonstrated. Using XGM, we have successfully implemented short-pulse wavelength conversion over 10 THz and error-free data conversion of a 2.5-Gb/s data sequence over 7.5 THz. The pulsed XGM experiments suggest that adjacent regions within an inhomogeneously broadened gain spectrum are partially coupled which increases the operational bandwidth, but at the expense of speed.     

Differential frequency shift of picosecond pulse four-wave mixingin semiconductor optical amplifiers

A numerical investigation of picosecond optical pulse four-wave mixing in semiconductor optical amplifiers has been undertaken to evaluate differential frequency shifting. This phenomenon appears as a shift of the central frequencies of the pump, probe and conjugate pulses during the mixing processes. The differential frequency shift is highly dependent upon the probe-pump frequency detuning and becomes more significant for shorter pulsewidths and higher pulse energies. It is also established that the differential frequency shifts between the pump, probe and conjugate pulses are different     

Unrepeatered video transmission using pulse frequency modulation over 100 km of monomode optical fibre

Unrepeatered transmission of 625-line colour video signals using PFM over monomode optical fibre is reported. The results show that a received video signal/noise ratio better than 53 dB unified weighted was achieved over 68 km of fibre at 1.3 ?m and 102 km at 1.52 ?m.     

Polarization-independent wavelength conversion at 2.5 Gb/s by dual-pump four-wave mixing in a strained semiconductor optical amplifier

We give a general expression for the polarization dependence of the four-wave mixing (FWM) efficiency in the dual-pump configuration. This expression, along with some general properties of the FWM susceptibility tensor, is used to propose a simple scheme to generate a nearly (1.5-dB variation) polarization independent FWM converted signal. The viability of this scheme is verified in a wavelength conversion experiment at 2.5 Gb/s.     

一种新的四波混频全光波长变换实验研究

优化设计半导体光纤环形激光器产生波长连续可调谐窄线宽的激光输出,可调谐范围为４０ｎｍ。利用半导体光放大器的非线性效应四波混频,实现了码速为２．５Ｇｂｉｔ／ｓＳＤＨ信号光的波长变换,向上变换８．２４ｎｍ,向下变换１９．４９ｎｍ。在实验中不需要外加泵浦光源。     

Polarization-insensitive wavelength conversion up to 10 Gb/s basedon four-wave mixing in a semiconductor optical amplifier

Polarization-insensitive wavelength conversion at 2.5 and 10 Gb/s using four-wave mixing in a bulk semiconductor optical amplifier is reported. At 10 Gb/s, a conversion range from 6.4-nm wavelength downshift to 4.8-nm upshift has been demonstrated. The conversion efficiency and signal-to-noise ratio versus conversion range are also characterized     

Effect of birefringence in a bulk semiconductor optical amplifieron four-wave mixing

We present experimental results on birefringence effects in an InGaAsP bulk semiconductor optical amplifier (SOA). Although the gain of the device is polarization insensitive, we observed a strong variation of the four-wave mixing (FWM) efficiency if the parallel input polarization of pump and signal wave was changed with respect to the device structure. This variation, which is attributed to birefringence in the SOA, can be as high as 10 dB for frequency detunings of about 6 THz. Thus, it might strongly affect the various applications of FWM for optical signal processing and parameter extraction. In addition, we performed polarization resolved measurements of the amplified spontaneous emission demonstrating different group velocity indices for TE and TM polarized light     

Continuously tunable wavelength converter by four-wave mixing in SBS suppressed highly nonlinear fibre

A simple and efficient continuously tunable wavelength converter for any arbitrary input and output wavelengths is presented. Conversion efficiency higher than -5-dB over 30-nm, owing to a dispersion-decreasing highly nonlinear fibre with stimulated Brillouin scattering (SBS) suppressed by distributed strain, is reported.     

160-Gb/s optical sampling by gain-transparent four-wave mixing in asemiconductor optical amplifier

We report on a broad-band all-optical switch that exhibits high linearity (>30 dB), high switching contrast (>25 dB), and large data wavelength tunability (100 nm). The switching principle is based on four-wave mixing. Two control pulse trains are placed in the gain wavelength region of a 1300-nm semiconductor-optical amplifier. The data signal, however, is at 1550 nm in the transparent wavelength region where four-wave mixing sidebands are generated due to index modulations. The switch is used to sample a 160-Gb/s data signal with a temporal resolution of approximately 1.7 ps