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Journal ArticleDOI

Switches and frequency converters based on cross-gain modulation in semiconductor optical amplifiers

01 Jun 1997-IEEE Photonics Technology Letters (IEEE)-Vol. 9, Iss: 6, pp 749-751
TL;DR: In this article, the large-signal theory of frequency converters based on cross-gain and cross-phase modulations in a semiconductor optical amplifier is developed, for the case in which pump and probe are injected from the same facet (co-propagating case).
Abstract: The large-signal theory of frequency converters based on cross-gain and cross-phase modulations in a semiconductor optical amplifier is developed, for the case in which pump and probe are injected from the same facet (co-propagating case). Simple expressions for the bandwidth of cross-gain modulation are derived for single and cascaded SOA's, and large-signal simulations are carried out for cascaded SOA's, pointing out some important system issues. In the cascaded case, the effect of the loss between the SOA's is highlighted.
Citations
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Journal ArticleDOI
TL;DR: In this paper, an analytical theory describing all-optical wavelength converters based on cross-gain modulation (XGM) in semiconductoroptical amplifiers is derived, which consists of two parts: a large-signal analysis yielding the transmission function for the signal, and a small signal analysis in order to describe the transformation of the signal and probe intensity noise.
Abstract: An analytical theory describing all-optical wavelength converters based on cross-gain modulation (XGM) in semiconductor-optical amplifiers is derived. Our theory consists of two parts: a large-signal analysis yielding the transmission function for the signal, and a small-signal analysis in order to describe the transformation of the signal and probe intensity noise. Both the large-signal as well as the small-signal theory reveal similar performance for the co- and the counterpropagating injection scheme for bit rates up to 2.5 Gb/s. This is confirmed by computer simulations. Consequently, the counterpropagating configuration is preferable because the implementation is simpler and conversion to the same wavelength is possible. In order to increase the conversion efficiency it is better to reduce the average signal power than to increase the probe power, which additionally reduces the output power range. However, there is a tradeoff between conversion efficiency and output extinction ratio. According to the small-signal analysis, the relative-intensity noise (RIN) due to the probe and due to the amplified spontaneous emission is negligible. Moreover, the converted signal has a lower RIN than the input signal.

114 citations


Cites background from "Switches and frequency converters b..."

  • ...This means that the output extinction ratio can be evaluated from the static transmission function . It should be noted that the large-signal theory can easily be extended to arbitrary bit rates since (5) and (6) are the same in a retarded time frame [ 23 ]....

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Journal ArticleDOI
TL;DR: In this paper, a small-signal analysis of all-optical switches based on a single semiconductor optical amplifier followed by an optical filter is presented, where the authors obtain analytical expressions for the optimum phase bias of the MZ interferometer filter and the resulting optical modulation bandwidth.
Abstract: A small-signal analysis of all-optical switches based on a single semiconductor optical amplifier followed by an optical filter is presented. Using the asymmetric Mach–Zehnder interferometer, which is the filter employed in the delayed-interference signal converter, as an example, we explain the principle of modulation bandwidth enhancement using optical filtering. We obtain analytical expressions for the optimum phase bias of the Mach–Zehnder interferometer filter and the resulting optical modulation bandwidth. By adopting a spectral approach, where the small-signal modulated field envelope is analyzed, we are able to generalize these results and calculate the bandwidth enhancement provided by an arbitrary filter.

82 citations

Journal ArticleDOI
TL;DR: In this paper, a theoretical analysis of the modulation response of a semiconductor laser amplifier is presented, where the role of the waveguide (scattering) loss is investigated in detail and is shown to influence the qualitative behavior of the response.
Abstract: We present a theoretical analysis of the modulation response of a semiconductor laser amplifier. We find a resonance behavior similar to the well-known relaxation oscillation resonance found in semiconductor lasers, but of a different physical origin. The role of the waveguide (scattering) loss is investigated in detail and is shown to influence the qualitative behavior of the response. In particular, it is found that a certain amount of waveguide loss may be beneficial in some cases. Finally, the role of the microwave propagation of the modulation signals is investigated and different feeding schemes are analyzed. The nonlinear transparent waveguide, i.e., an amplifier saturated to the point where the stimulated emission balances the internal losses, is shown to be analytically solvable and is a convenient vehicle for gaining qualitative understanding of the dynamics of modulated semiconductor optical amplifiers.

79 citations


Cites background from "Switches and frequency converters b..."

  • ...The large gain of long amplifiers reduces the stimulated carrier lifetimes to values of the order of tens of picoseconds and propagation effects also increase the amplifier bandwidth [9], [10]....

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Journal ArticleDOI
TL;DR: In this article, a new scheme for all-optical signal reshaping is proposed, which is based on four-wave mixing (FWM) in dispersion-shifted fiber (DSF).
Abstract: A new scheme for all-optical signal reshaping is proposed. It is shown that proper adjustment of the operating conditions of a wavelength converter based on four-wave mixing (FWM) in dispersion-shifted fiber (DSF) results in significant extinction ratio enhancement and noise suppression of the converted signal. The key issue in the proposed idea is the application of the modulation bitstream on the input pump wave. Detailed numerical simulation shows that it is possible to achieve a wavelength-converted output with extinction ratio of 20 dB when the extinction ratio of the input signal is 10.5 dB, while at the same time, the improvement in the Q-factor is almost 6 (from 6.5 at the input, it becomes more than 12 at the output). The theoretical predictions have been experimentally confirmed by measuring the transfer function of the FWM in a 17-km-long DSF under different operating conditions. The obtained results are in a very good agreement with those predicted theoretically.

71 citations


Cites methods from "Switches and frequency converters b..."

  • ...Well-established methods for all-optical wavelength conversion based on the use of semiconductor optical amplifier (SOA) as an active nonlinear medium are cross-gain modulation [1], [2] cross-phase modulation [2], and four-wave...

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Journal ArticleDOI
TL;DR: In this article, a novel scheme that exploits cross-gain modulation (XGM) in semiconductor optical amplifiers (SOAs) without overall pattern effects is presented. But this technique uses two signals with reversed-intensity modulation and different wavelength to exploit propagation and gain-compression dynamics in gain-saturated SOAs at almost constant overall input power.
Abstract: In this paper, we present a novel scheme that exploits cross-gain modulation (XGM) in semiconductor optical amplifiers (SOAs) without overall pattern effects. This technique uses two signals with reversed-intensity modulation and different wavelength to exploit propagation and gain-compression dynamics in gain-saturated SOAs at almost constant overall input power. The resulting cross-gain-compression mechanism between copropagating waves can lead to all-optical waveform reshaping. By using this technique, we experimentally demonstrate enhanced wavelength conversion by XGM and wavelength-preserving noise compression at 10 Gb/s

59 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the effect of the shape and the initial frequency chirp of input pulses on shape and spectrum of amplified pulses is discussed in detail and the case in which the input pulsewidth is comparable to the carrier lifetime so that the saturated gain has time to recover partially before the trailing edge of the pulse arrives.
Abstract: Amplification of ultrashort optical pulses in semiconductor laser amplifiers is shown to result in considerable spectral broadening and distortion as a result of the nonlinear phenomenon of self-phase modulation (SPM). The physical mechanism behind SPM is gain saturation, which leads to intensity-dependent changes in the refractive index in response to variations in the carrier density. The effect of the shape and the initial frequency chirp of input pulses on the shape and the spectrum of amplified pulses is discussed in detail. Particular attention is paid to the case in which the input pulsewidth is comparable to the carrier lifetime so that the saturated gain has time to recover partially before the trailing edge of the pulse arrives. The experimental results, performed by using picosecond input pulses from a 1.52- mu m mode-locked semiconductor laser, are in agreement with the theory. When the amplified pulse is passed through a fiber, it is initially compressed because of the frequency chirp imposed on it by the amplifier. This feature can be used to compensate for fiber dispersion in optical communication systems. >

1,175 citations


"Switches and frequency converters b..." refers methods in this paper

  • ...We will follow here, an extension of the approach of [6]....

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Journal ArticleDOI
D.A.O. Davies1
TL;DR: In this article, the authors analyzed the wavelength conversion due to gain saturation in a traveling wave semiconductor laser amplifier using a small-signal model and showed that the small-Signal bandwidth of wavelength conversion is not limited simply to the carrier modulation bandwidth, but also depends on the single-pass gain of the device.
Abstract: Wavelength conversion due to gain saturation in a travelling wave semiconductor laser amplifier is analyzed using a small-signal model An analytic expression is developed showing that the small-signal bandwidth of wavelength conversion is not limited simply to the carrier modulation bandwidth, but also depends on the single-pass gain of the device >

59 citations


"Switches and frequency converters b..." refers background in this paper

  • ...of a SOA with waveguide loss [4], [7], it has no overshoot, and its 3-dB frequency given by the remarkably simple expression:...

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Journal ArticleDOI
TL;DR: In this article, the exact closed form solution of the coupled-mode equations describing frequency converters based on cross-gain modulation in semiconductor optical amplifiers is given, and it is shown that the frequency response of the converter is strongly affected by the waveguide internal loss.
Abstract: We give the exact closed form solution of the coupled-mode equations describing frequency converters based on cross-gain modulation in semiconductor optical amplifiers. We show that the frequency response of the converter is strongly affected by the waveguide internal loss.

50 citations


"Switches and frequency converters b..." refers background in this paper

  • ...of a SOA with waveguide loss [4], [7], it has no overshoot, and its 3-dB frequency given by the remarkably simple expression:...

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Journal ArticleDOI
TL;DR: In this paper, the authors show experimentally and theoretically that the bandwidth for wavelength conversion through cross-gain modulation varies approximately linearly with the length of the amplifier, and that by cascading two similar semiconductor optical amplifiers, the small-signal wavelength conversion bandwidth is doubled.
Abstract: The authors show experimentally and theoretically that the bandwidth for wavelength conversion through cross-gain modulation varies approximately linearly with the length of the amplifier. By cascading two similar semiconductor optical amplifiers, the small-signal wavelength conversion bandwidth is doubled.

42 citations


"Switches and frequency converters b..." refers background in this paper

  • ...The net effect is to limit the bandwidth for XGM, as discussed in [1], [2]....

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  • ...In contrast, it has been shown [1], [3]–[5] that, in some cases, the copropagating setup may enhance the speed of the device, and...

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11 Jul 1996

9 citations


"Switches and frequency converters b..." refers background in this paper

  • ...The net effect is to limit the bandwidth for XGM, as discussed in [1], [2]....

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  • ...At high bit rates, it will also be necessary to take into account the ultrafast carrier heating and spectral hole burning effect [2]....

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  • ...Although error-free wavelength conversion at a bit rate close to the small-signal bandwidth can be performed [2], if several wavelength conversion stages are required, or if the requirements on the pulse rise and fall times of the converted signal are stringent, the maximum allowable bit rate may only be typically a tenth of the small-signal bandwidth....

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