Transmission of optical communication signals by distributed parametric amplification

We have demonstrated, for the first time to our knowledge, distributed parametric amplification, i.e. amplification of 10-Gb/s communication signals along a 75-km transmission fiber by using a co-propagating pump with only 66.5 mW of power.published_or_final_versio

Recent advances in the design and implementation of practical fiber optical parametric amplifiers

Conference on Optoelectronic and Microelectronic Materials and Devices, Brisbane, Australia, 8-10 December 2004Fiber optical parametric amplifiers (OPAs) are based on the third-order nonlinear susceptibility of glass fibers. If two strong pumps and a weak signal are fed into a fiber, an idler is generated. Signal and idler can grow together if pump power is high enough, and phase matching occurs. In recent years, impressive performance has been demonstrated in several respects: 1) Gain in excess of 60 dB has been obtained; 2) fiber OPAs can exhibit a large variety of gain spectra: a gain bandwidth of 400 nm has been demonstrated; tunable narrowband gain regions can also be generated; 3) Noise figure of 3.7 dB, limited by other third-order nonlinear process; 4) Polarization-insensitive operation in both one-pump and two-pump configurations; 5) The presence of the idler can be used for wavelength conversion. Also, the spectrum of the idler is inverted with respect to that of the signal; thus by placing an OPA in the middle of a fiber span one can realize mid-span spectral inversion (MSSI) which counteracts the effect of fiber dispersion and some nonlinear effects. Besides using fiber OPA in continuous-wave regime as in typical systems, pulsed-pump has also been demonstrated to achieve larger bandwidth and higher peak gain by combining with optical filtering technique. Furthermore, by modulating the pump it is possible to modulate signal and/or idler at the output. This can be used to implement a variety of signal processing functions, including: fast signal switching; demultiplexing of time-division-multiplexed signals; retiming and reshaping of waveforms; optical sampling. A number of challenges must be overcome in order for fiber OPAs to be useful in communication applications. In multi-wavelength systems, these are: four-wave mixing, cross-phase modulation; and cross-gain modulation between signals. Furthermore, the pump-to-signal relative intensity noise (RIN) transfer and frequency/phase modulation (FM/PM) to signal intensity conversion are also potential challenges for practical fiber OPAs. © 2005 IEEE.published_or_final_versio

Pump-to-signal transfer of low-frequency intensity modulation in fiber optical parametric amplifiers

This paper describes the theoretical and experimental investigation of the transfer of low-frequency intensity modulation (IM) from pump to signal in fiber optical parametric amplifiers (OPAs). It is first established that low-frequency IM of the pump remains unchanged over the length of the amplifier in spite of the presence of parametric gain. The pump-power dependence of the OPA gain is then used to calculate the instantaneous effect of pump IM on the signal and idler output powers. These calculations are performed for both one- and two-pump OPAs. The main predictions are that 1) the ratio ρ of the signal intensity modulation depth to that of the pump varies across the OPA gain spectrum and 2) for a 20-dB gain, ρ can exceed 10 at some wavelengths, which indicates that this effect can be detrimental. Experiments have been performed to verify these predictions. Using sinusoidal IM of the pump, the resulting amplified signal IM was measured, and the experimental results were found to be in good agreement with the theoretical predictions. © 2005 IEEE.published_or_final_versio

Quasi-passive and reconfigurable optical node: implementations with discrete latching switches

Quasi-Passive and Reconfigurable (QPAR) optical nodes are implemented using two different discrete optical latching switches based on Micro-Opto-Mechanical and Magneto-Optic principles. A clear trade-off between speed and power consumption is noticed for those QPAR realizations

Prospects for CW fiber OPAs and OPOs

We review the characteristics of CW fiber OP As, and their application to CW fiber OPOs. These can exhibit low threshold, high conversion efficiency, multi-Watt output power, tunability, and single-frequency operation, from visible to mid-IR. © 2003 Optical Society of America.link_to_subscribed_fulltex

Wide-Band Tuning of the Gain Spectra of One-Pump Fiber Optical Parametric Amplifiers

By suitably choosing the fiber properties, and by tuning the pump wavelength near the fiber zero-dispersion wavelength, one can in principle generate a wide variety of one-pump fiber optical parametric amplifier gain spectra. These can range from a very wide single region to two symmetric narrow gain regions far away from the pump. We have experimentally verified these predictions. With a highly nonlinear fiber, we have inferred the existence of gain over a single 400-nm region and measured a maximum on-off gain of 65 dB. With a common dispersion-shifted fiber, we have obtained tunable gain regions less than 1 nm wide, up to 200 nm from the pump; we have also shifted these by several nanometers by lowering the fiber temperature to 0°C.published_or_final_versio

50-dB nonlinear crosstalk suppression in a WDM analog fiber system by complementary modulation and balanced detection

We investigate, theoretically and experimentally, a novel scheme to suppress the nonlinear crosstalk between wavelengths in wavelength-division multiplexing (WDM) analog fiber systems. It is based on an improvement to a previously introduced crosstalk-suppression technique by complementary modulation of two closely spaced optical twin carriers (TCs). By combining the modulated TCs by a balanced detector (TCs-balanced detection [TC-BD]), the suppression can be improved further. We have obtained up to 50-dB crosstalk reduction at low modulation frequencies, where crosstalk is most severe, and in the most interesting region for cable television systems.link_to_subscribed_fulltex

Parametric amplification in optical fibers with random birefringence

By averaging the OPA equations for fibers with random birefringence, we show that the gain coefficient with orthogonal pumps is significantly larger than would be expected in nonbirefringent fibers. This is verified by experiments. © 2003 Optical Society of America.link_to_subscribed_fulltex

Temperature control of the gain spectrum of fiber optical parametric amplifiers

The gain spectrum of a fiber optical parametric amplifier (OPA) can be controlled by imposing a temperature distribution along the fiber, which modulates the local fiber zero-dispersion wavelength λ 0 and hence the parametric gain coefficient. We present simulations and experimental verification for various binary temperature distributions. The method should be applicable to fibers with realistic longitudinal variations of λ 0. © 2005 Optical Society of America.link_to_subscribed_fulltex

Fiber optical parametric amplifiers with linearly or circularly polarized waves

We introduce a formalism that provides a unified solution for the gain spectrum of fiber optical parametric amplifiers (OPAs) using either linearly or circularly polarized waves. There are 12 basic types, including five that have not been previously investigated to our knowledge. We provide a simple method for calculating the maximum gain and nonlinear phase mismatch for such OPAs. All these OPAs have similar elliptical graphs for parametric gain versus propagation constant mismatch, with a width equal to four times the height. This implies that, when fiber dispersion is taken into account, any two-pump OPA can be used to obtain the same gain spectrum as any other OPA in the same fiber, provided that the pump power is adjusted for equal maximum gain and that real solutions exist for the resulting equation for the required pump spacing. In that sense, all these fiber OPAs form an equivalence class.link_to_subscribed_fulltex