Traveling-wave Optical Amplifier Research Articles

Simulative study on the cascaded stages of traveling wave semiconductor optical amplifiers based multiplexing schemes for fiber optic systems improvement

Abstract This study has outlined the performance analysis of the cascade traveling-wave optical amplifier (Semiconductor optical amplifier [SOA]) with multiplexing techniques based on fiber communication transceiver systems. The maximum Quality factor is measured against signal power. Signal input power level is enhanced by using the suggested model with previous model. The low pass Bessel filter removes the unwanted ripples from the original signal. The suggested model has clarified better performance efficiency than the previous model.

450 nm (Al,In)GaN optical amplifier with double 'j-shape' waveguide for master oscillator power amplifier systems.

In this paper we demonstrate 450 nm (Al,In)GaN graded index separate confinement heterostructure travelling wave optical amplifier with a double 'j-shape' waveguide. The length of the amplifier is 2.5 mm and the width of the ridge is 2.5 µm. The active region consists of three 3.5 nm thick quantum wells. The measured optical gain under CW operation in room temperature exceeded 29 dB for low power input signals. The saturation output power was 21 dBm for 400 mA driving current. The demonstrated amplifier, provides a good solution for the blue light, all nitrides, and master oscillator power amplifier systems.

A new method of restraining the Fabry–Perot resonance

In the paper, we present a new method of restraining the Fabry-Perot resonance. The method is to combine dip angle with taper angle in the structure of the device and avoids the process of antireflection coatings. The experimental results show that restraining effect is apparent. A high threshold current has been obtained for the sample with both dip angle and taper angle structure. It provides a new method to make traveling-wave optical amplifiers.

Monolithic integration of a quantum-well laser and an optical amplifier using an asymmetric twin-waveguide structure

We demonstrate the monolithic integration of a 1.55 μm wavelength InGaAsP-InP multiple-quantum-well (MQW) laser and a traveling-wave optical amplifier using an asymmetric, vertical twin-waveguide structure. The laser and amplifier share the same strained InGaAsP MQW active layer grown by gas-source molecular beam epitaxy, while the underlying passive waveguide layer is used for on-chip optical interconnections between the active devices. The asymmetric twin-waveguide structure uses the difference in modal gains to discriminate between the even and odd modes.

Gain saturation in traveling-wave semiconductor optical amplifiers

The gain saturation behavior of semiconductor traveling-wave optical amplifiers has been analyzed using a model that includes the specific dependence of gain on carrier concentration. Under the condition of a specific gain at a particular current, it is found that the saturation power strongly depends on the choice between quantum well (QW) or bulk amplifying medium but weakly on the detailed design of the device such as the number of QW's or the thickness of the bulk layer. The higher saturation power of the QW-based amplifier is caused by its logarithmic gain-current relation rather than its low optical confinement factor. Also, when the unsaturated device gain is specified, the designed saturation power can be obtained with the lowest drive current by using the highest optical confinement.

Frequency converters based on FWM in traveling-wave optical amplifiers: Theoretical aspects

Abstract We summarize the results of a theoretical model, developed to investigate the performance of a frequency converter based on four-wave mixing in a bulk traveling wave amplifier. The theory predicts very high values of conversion efficiency and signal-to-background ratio in the bandwidth of the converted signal. These results, whose experimental confirmation is reported elsewhere, increase the potential of using four-wave mixing in semiconductor amplifiers in actual optical systems.

Temporal Response of Semiconductor Travelling Wave Optical Amplifiers to an Exponentially Varying Input Signal

Abstract A theoretical treatment of the propagation of optical signals through semiconductor travelling wave amplifiers (TWAs) is presented. Analytic solutions are obtained for the temporal behaviour of the output for amplifiers subject to input signals composed of an exponentially varying small signal superimposed on a large time-independent signal. The formulation includes the spontaneous recombination term and the line-width enhancement (anti-guiding) factor. The solution obtained may be readily interpreted as a combined amplitude and phase modulated output signal. The analysis also clearly reveals the combined effects of the spontaneous recombination rate and the time constant of the exponentially varying input signal. In this way a total description of the response of the optical amplifier is obtained.

Optical digital cross‐connect system using photonic switch matrices and optical amplifiers

AbstractAn optical digital cross‐connect system (DCS) comprised of both photonic switching networks and electric DCSs is proposed for applications in network‐failure restorations. Optical DCSs exhibit excellent characteristics in restorations of multiple failures and when compared against their electrical counterparts, size‐reduced apparatus can be expected. the design of DCSs for applications in metropolitanarea networks are investigated and it is shown that such DCSs can be realized using LiNbO3 photonic switch matrices together with traveling wave optical amplifiers (TWA).With respect to the problem arising from the polarization dependency of TWA gain, it was solved using the output power controller (APC) which is shown theoretically to cause no difficulty in the noise characteristics. the optical DCS is designed and manufactured using LiNbO3 switch matrices and TWA, by which its basic operation properties are verified. Using this trial system, it is confirmed that the network failures can be restored by changing the optical routes.

Broadband wavelength conversion with amplification by four-wave mixing in semiconductor travelling-wave amplifiers

The authors demonstrate for the first time broadband wavelength conversion with amplification by four-wave mixing in semiconductor travelling-wave optical amplifiers and verify the cubic dependence of wavelength conversion efficiency on the amplifier's single-pass optical gain.

Optical digital cross-connect system using photonic switch matrices and optical amplifiers

This paper presents, for potential application to network failure restoration, an optical digital cross-connect system (DCS) which uses both a photonic switching network and an electric DCS. It is shown that a system constructed of LiNbO/sub 3/ 8/spl times/8 switch matrices and semiconductor traveling-wave optical amplifiers (TWA's) could be applied to metropolitan area networks. An experimental optical DCS system has been designed and fabricated which incorporates both LiNbO/sub 3/ switch matrices and TWA's, and with it, line-failure restoration, a fundamental operation of optical DCS, has been successfully demonstrated. >

Integrated MQW optical amplifier/noise-filter/photodetector photonic circuit

A monolithically integrated photonic circuit with an InGaAs/InGaAsP multiple-quantum-well (MQW) traveling-wave optical amplifier, a Bragg reflection grating-folded noise filter, and an MQW photodetector has been demonstrated. This photonic circuit offers potential as a preamplified lightwave receiver in high-data-rate applications because of its compactness and potentially low cost. >

InGaAs/InGaAsP MQW optical amplifier integrated with grating-assisted vertical-coupler noise filter

A photonic integrated circuit with an InGaAs/InGaAsP multiple-quantum-well (MQW) traveling-wave optical amplifier and a grating-assisted vertical-coupler filter as a noise filter have been demonstrated. A fiber-to-amplifier/filter gain of approximately 0.5 dB and a 3-dB filter bandwidth (FWHM) of approximately 70 AA at 1.56 mu m filter center wavelength have been achieved. This photonic circuit is potentially suitable as a building-block for preamplifier lightwave receivers or high-gain, high-power optical amplifiers which are essential for optical communication systems and lightwave networks.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

20-nm optical wavelength conversion using nondegenerate four-wave mixing

Wavelength conversion of optical signals over 20 nm is demonstrated using highly nondegenerate four-wave mixing in a semiconductor traveling-wave optical amplifier. This technique has the potential for extremely-high-speed operation and allows continuous tuning of both input and output wavelengths over the amplifier gain bandwidth. It is demonstrated that, even for such a large wavelength conversion range, it is possible to obtain conversion efficiencies in excess of -10 dB and high extinction ratios. The feasibility of the technique is demonstrated by system measurements at 622 Mb/s, showing a 1.1-dB power penalty at 10/sup -9/ bit error rate (BER). >

Highly nondegenerate four-wave mixing and gain nonlinearity in a strained multiple-quantum-well optical amplifier

Highly nondegenerate four-wave mixing was investigated in a 1.5 μm compressively strained multi-quantum-well semiconductor traveling-wave optical amplifier at detuning frequencies up to 600 GHz. A gain nonlinearity with a characteristic relaxation time of 650 fs was determined from the data, and the nonlinear gain coefficient was estimated to be 4.3×10−23 m3. Dynamic carrier heating is believed to be the major source of nonlinear gain in this device at the wavelengths investigated.

Strict calculation of the light statistics at the output of a travelling wave optical amplifier

A new method for calculating the probability density function of the photon number propagating through a travelling wave optical amplifier with no restriction on its working regime (linear and nonlinear) is reported. The Letter shows that the widely used Gaussian approximation of the probability density function does not match the real statistics if the incident optical power is small.

A probabilstic model of traveling wave optical amplification

A probabilistic model for traveling wave optical amplifiers is presented. Optical signal and noise are assumed to be bunches of photons traveling along the active region with size varying accordingly to simple random rules. The theory leads to the complete statistical characterization of signal and noise as marked Poisson processes. In spite of the fact that its validity is confined to small-signal regimes, the result may be very useful for a more accurate performance evaluation and design criteria of optical transmission systems using recently developed erbium-doped fiber amplifiers.

Analytical solution of amplitude and phase modulation in semiconductor traveling-wave optical amplifiers subject to transient optical signals

We present a formalism and a technique for analyzing the propagation of optical signals through semiconductor traveling-wave amplifiers. The formalism retains, in particular, the spontaneous recombination term, and the newly developed technique permits analytic, real-time solutions to be obtained, so that both the transient and the steady-state regimes are characterized. This end has been achieved by iteratively applying the method of in order to solve the set of coupled differential equations that result from the formulation of the characteristics physical problem. From the real-time solutions so obtained it is also possible easily to recognize the amplitude and phase-modulation effects that occur not only in the steady state but also in the transient regime.

Picosecond pulse generation from a 1.3 mu m distributed feedback laser diode using soliton-effect compression

An experimental demonstration of the soliton-effect pulse compression with a 1.3- mu m distributed feedback (DFB) semiconductor laser, a compression fiber, two traveling-wave optical amplifiers, and a soliton-effect compression fiber is presented. The experimental configuration and the details of the pulse generation from a gain-switched 1.3- mu m DFB laser diode are described. Results of temporal compression using a fiber of normal dispersion are presented where reduction of the pulsewidth to 2.45 ps is realized. The pulse amplification characteristics of a two-stage traveling-wave semiconductor laser amplifier are discussed with emphasis on the observed temporal broadening and spectral narrowing. After a brief description of the soliton-effect compression in an optical fiber, details of the experimental realization are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Group delay and alpha -parameter measurement of 1.3 mu m semiconductor traveling-wave optical amplifier using the interferometric method

The group delay dispersion and the linewidth broadening factor ( alpha -parameter) are measured for a 1.3- mu m semiconductor traveling-wave optical amplifier (TWA) using a newly developed interferometric method. By Fourier transforming an interferometric cross-correlation signal, both the optical phase and the gain are simultaneously obtained in the entire gain bandwidth. The group delay spectrum is evaluated from the frequency derivative of the phase, and by selecting an appropriate interval for the interferometer scan, a refractive index dispersion of approximately 3.2 fs/nm is separated from the dispersion caused by Fabry-Perot resonance. From the phase and gain change with injection current, the alpha -parameter spectrum is evaluated, and the results indicate a strong dependence on wavelength.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Experimental gain and saturation performance of GaAs/AlGaAs SCH quantum well travelling wave optical amplifier

Successful combination of high gain and high saturation output power performance in a GaAs/AlGaAs quantum well travelling wave amplifier is reported. Comparable performance to similar 1.5 mu m InGaAs/InP devices is achieved, surpassing expectations. A device with a three quantum well active region and separately confined heterostructure design has both a small signal gain of 22.9 dB and a saturation output power of 40 mW at the low drive current of 40 mA. >