Depolarization technique for wavelength conversion using four-wave mixing in a dispersion-flattened photonic crystal fiber

Department of Electronic Engineering, The Chinese University of Hong Kong, Hong Kong, 00, Hong Kong
Optics Express (Impact Factor: 3.49). 08/2005; 13(14):5409-15. DOI: 10.1364/OPEX.13.005409
Source: PubMed


We have developed a depolarization technique to achieve polarization-insensitive wavelength conversion using four-wave mixing in an optical fiber. A maximum conversion efficiency of -11.79 dB was achieved over a 3 dB bandwidth of 26 nm in a 100-m-long dispersion-flattened photonic crystal fiber. The polarization-dependent conversion efficiency was less than 0.38 dB and the measured power penalty for a 10 Gbit/s NRZ signal was 1.9 dB. The relation between the conversion efficiency and the degree of polarization of the pump was also formulated.

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    • "Another method to overcome the polarization dependence is polarization diversity, in which the pump is split into two orthogonal states that independently interact with the data [16]–[20]. A related approach is to depolarize the pump pulse train, which requires a fiber delay that is longer than the coherence length of the pump laser [21]. "
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    ABSTRACT: We present a theoretical, numerical, and experimental investigation of the polarization dependence of cross-phase modulation in nonlinear birefringent fibers. Two new methods are described for producing a polarization-independent spectral shift through cross-phase modulation of a weak probe signal by a copropagating strong optical pulse. The birefringence of the fiber and spectral separation between the pump and probe signals are shown to play a critical role in determining the polarization dependence of the cross-phase modulation process. The methods are experimentally verified in two different highly nonlinear fibers, and are used to achieve polarization-independent optical switching at speeds of up to 160 Gb/s.
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    • "One problem with fiber-based nonlinear devices is that they typically depend on the input polarization state, which can vary unpredictably in installed fiber systems. In response to this, a number of schemes have been proposed such as polarization diversity [4], twisting of the nonlinear fiber [5], [6], and depolarization of the clock pulses [7]. Any of these can eliminate the polarization dependence, but generally require added complexity in the device. "
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    • "HE polarization dependency has been one of serious problems in optical sensing, measurement [1], and communication systems [2]. In order to eliminate the polarization dependency , some types of depolarizers are widely used. "
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    ABSTRACT: A new fiber depolarizer employing a polarization beam splitter loop structure is proposed and demonstrated. The depolarizer is devised for broad-band operation and the depolarization of narrow linewidth light source without any help of polarization controllers or Faraday rotator mirrors. A polarizing method is developed that shows good performance without polarization control unit. Therefore, the proposed depolarizer can be cost-effective and easily configured. From experiments, low output degree of polarization less than 10% is obtained for a narrow linewidth light source.
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