Performance Of Semiconductor Optical Amplifier Research Articles

All-optical reservoir computing system based on polarization dynamics

Reservoir computing (RC) is a simplified recurrent neural network and can be implemented by using a nonlinear system with delay feedback, thus it is called delay-based RC. Various nonlinear nodes and feedback loop structures have been proposed. Most of existing researches are based on the dynamical responses in intensity of the nonlinear systems. There are also a photoelectric RC system based on wavelength dynamics and an all-optical RC based on the phase dynamics of a semiconductor laser with optical feedback, as well as so-called polarization dynamics of a vertical cavity surface emitting laser (VCSEL). However, these VCSEL-RCs actually are based on the intensity dynamics of two mutually orthogonal polarization modes, or polarization-resolved intensity dynamics. The RC based on rich dynamical responses in polarization has not yet been found. A semiconductor optical amplifier (SOA) fiber ring laser can produce rich dynamical states in polarization, and is used in optical chaotic secure communication and distributed optical fiber sensing. To further expand the application of polarization dynamics of the SOA fiber ring laser and open up a new direction for the research of optical RC neural network, an all-optical RC system based on polarization dynamics of the ring laser is proposed. The ring laser is used as the reservoir, and the SOA as the nonlinear node. After the input signal is masked according to a synchronization scheme, it is injected into the reservoir by intensity modulation for a continuous wave generated by a superluminescent light emitting diode (SLED). The dynamical response in polarization of the ring laser is detected by a polarizer and a photodetector. The influences of the SOA operation current, output power of the SLED and attenuation of a variable optical attenuator (VOA) in the fiber loop on the polarization dynamic characteristic (mainly referring to the output degree of polarization) of the laser are analyzed experimentally. The fading memory and nonlinear response of the RC system based on the polarization dynamic response and intensity dynamic response are compared experimentally. The influences of output power of the SLED and attenuation of the VOA on fading memory, consistency and separation of the RC system based on the two kinds of dynamic responses are investigated experimentally. Thus the range of the VOA attenuation is determined. The network performance of the polarization dynamics RC system is evaluated by processing a Santa Fe time series prediction task and a multi-waveform recognition task. The normalized mean square error can be as low as 0.0058 for the time series prediction task, and the identification rate can be as high as 100% for the recognition task under the appropriate system parameters and only 30 virtual nodes. The experimental results show that the polarization dynamics RC system has good prediction performance and classification capability, which are comparable to the existing RC system based on intensity dynamics of the ring laser. The system can be expected to process two tasks in parallel when the polarization dynamics and intensity dynamics are used at the same time.

Temperature response of all-optical XOR logic function based on different semiconductor optical amplifiers

A critical area of research is studying the performance of semiconductor optical amplifiers (SOAs) at high temperatures. In this paper, the performance of all-optical exclusive-OR (XOR) logic gate is investigated at high operating temperatures (TOP) using different SOAs technologies such as conventional SOAs, carrier reservoir (CR)-SOAs, reflective SOAs (RSOAs), and photonic crystal (PC)-SOAs, for the first time to our knowledge. The time-dependent differential equations of SOAs, CR-SOA, RSOAs, and PC-SOAs at different operating data rates have been solved. The performance of the XOR logic gate is evaluated by calculating the quality factors and plotting the eye diagrams for each amplifier. Besides, the dependence of the key operating parameters on the TOP is examined and assessed for each scheme. The results showed that the RSOAs perform better at high temperatures than other proposed SOA technologies.

Reflective Semiconductor Optical Amplifier Direct Modulation Capability Enhancement Using Birefringent Fiber Loop

The feasibility of employing a birefringent fiber loop to enhance the performance of a directly modulated reflective semiconductor optical amplifier is experimentally demonstrated for the first time. The birefringent fiber loop acts as an optical filter of opposite slope than that of the reflective semiconductor optical amplifier electro-optical response and counteracts the finite reflective semiconductor optical amplifier modulation bandwidth of only 0.89 GHz. By proper adjustment of its detuning, the birefringent fiber loop tailors the spectral components that physically manifest due to the reflective semiconductor optical amplifier dynamic perturbation subject to direct modulation in the saturated gain regime, and suppresses the pattern-dependent distortions in the time domain. In this manner, the birefringent fiber loop manages to significantly improve the quality characteristics of the encoded signal at higher data rates than those enabled by the reflective semiconductor optical amplifier limited modulation capability. Owing to the birefringent fiber loop, the reflective semiconductor optical amplifier modulation range is extended to 4 Gb/s at the raw bit error rate of 1.0×10−9, and to 11 Gb/s at the forward error correction limit of 3.8×10−3. These results, which are unique against the evaluation criterion adopted in the first case, and the modulation speed achieved with post-filtering schemes in the second, highlight the beneficial role that the birefringent fiber loop can play in supporting reflective semiconductor optical amplifier operation for intensity amplification and modulation purposes.

High Power and High Efficiency Operation of Semiconductor Optical Amplifier Assisted Extended Reach Electroabsorption Modulated DFB Laser (AXEL) for Extension of Transmission Distance

High Power and High Efficiency Operation of Semiconductor Optical Amplifier Assisted Extended Reach Electroabsorption Modulated DFB Laser (AXEL) for Extension of Transmission Distance

Performance Evaluation of Optical Amplifiers for High-Speed Optical Networks

Abstract Optical networks were invented by the developing and developed nations in order to extend the capacity required for communication systems in a worthwhile way. In this paper, the attempt is done to improve the capacity and performance of semiconductor optical amplifier, Raman and erbium-doped fiber amplifier (EDFA) amplifiers used in optical networks. The potential of different optical amplifiers operating at 8×10 Gbps has been examined and their performance was compared on behalf of different parameters, viz. eye opening, eye closure, jitter, quality factor and transmission distances. It was observed that EDFA provided the consistent good quality of communication for long-distance transmission up to 150 km along with better eye opening and eye closure with acceptable jitter performance. Further, it is observed on the basis of quality factor and bit error rate that EDFA gives comparably better performance than Raman amplifier. Moreover, it is seen that as the data rate of the system increases, the quality of communication signals starts decreasing.

Theoretical Analysis of Directly Modulated Reflective Semiconductor Optical Amplifier Performance Enhancement by Microring Resonator-Based Notch Filtering

We demonstrate the feasibility of using a single microring resonator (MRR) as optical notch filter for enabling the direct modulation of a reflective semiconductor optical amplifier (RSOA) at more than tripled data rate than possible with the RSOA alone. We conduct a thorough simulation analysis to investigate and assess the impact of critical operating parameters on defined performance metrics, and we specify how the former must be selected so that the latter can become acceptable. By using an MRR of appropriate radius and detuning, the RSOA modulation bandwidth, which we explicitly quantify, can be extended to overcome the RSOA pattern-dependent performance limitations. Thus, the MRR makes the RSOA-encoded signal exhibit improved characteristics that can be exploited in practical RSOA direct modulation applications.

Widely tunable narrow-linewidth 1.5 μm light source based on a monolithically integrated quantum dot laser array

A monolithically integrated widely tunable narrow-linewidth light source was realized on an InP-based quantum dot (QD) gain material. The quasi zero-dimensional nature of QDs and the resulting low linewidth enhancement factor enabled standalone distributed feedback (DFB) lasers with intrinsic linewidths as low as 110 kHz. An integrated device comprising four DFB lasers with on-chip micro-heaters, a 3 dB-coupler network, and a semiconductor optical amplifier (SOA), which covers the entire C+ telecom band, exhibits a linewidth of below 200 kHz independent of the SOA operation current.

Experimental performance of semiconductor optical amplifiers and praseodymium-doped fiber amplifiers in 1310-nm dense wavelength division multiplexing system

One of the key optical transmission components is optical amplifiers. Studies on the amplification properties of the 1310-nm optical amplifiers are presented. The evaluated optical amplifiers are semiconductor optical amplifier (SOA) and praseodymium-doped fiber amplifier (PDFA). The study is aimed at the dynamic operation in single- and multiwavelength domains with high rate signals. The maximum obtained gain was 25.0 dB for SOA and 20.9 dB for PDFA. For the SOAs, the minimum achieved value of the receiver sensitivity was −11.5 dBm for a single channel and −11.5 dBm for a dense wavelength division multiplexing case while for PDFA those values were −11.0 dBm and −10.9, respectively. The main advantage of the PDFA in comparison to the measured SOAs is its higher saturation power. The SOAs proved to be viable candidates for high-speed amplification in the 1310-nm wavelength domain.

Semiconductor optical amplifiers in negative‐exponential fading: regenerators and pre‐amplifiers

In this study, the authors discuss the mitigation of negative-exponential fading in optical wireless communication systems. The mitigation technique involves the utilisation of a semiconductor optical amplifier (SOA) that, depending on the link arrangement, acts either as regenerator or pre-amplifier. As a regenerator, the SOA gain saturates during normal link operation and increases when the link experiences a fade. This unbalanced SOA operation serves towards the equalisation of the signal power at its output and fades become less severe and of reduced duration. The analytical results predict that the fade probability is reduced by over 90% and the scintillation index is improved by 75% for an optimal level of the received power. Moreover, the average duration of fades is also reduced by 68% for the same power level. As a pre-amplifier, the SOA modifies the noise statistics at the receiver and provides a static sensitivity increase of at least 10 dB at 10 Gb/s, depending on the bit-error-rate (BER) target. The analytical results show that this sensitivity improvement imparts a reduction of one order of magnitude on the average BER, of at least 94% on the outage probability and of at least 78% on the average duration of fades.

A Simultaneous Variable Optical Weight and Delay in a Semiconductor Optical Amplifier for Microwave Photonics

In this paper, we demonstrate how a single semiconductor optical amplifier can serve as a simultaneous variable optical weight and tunable optical delay for microwave photonics. The device weight, or power transmission, and delay can be controlled simultaneously and independently from each other by varying the input optical power and the semiconductor bias current. The dual functionality is achieved by combining the effects of slow and fast light with cross-gain modulation in the semiconductor. We experimentally demonstrate a tunable delay range of 100 ps and RF gain range of $-$ 6 to +3 dB for a 600-MHz microwave signal and show how the weight and delay of the device can be separately tuned. The delay range and bandwidth of the device are limited by the semiconductor carrier lifetime and characteristic of slow and fast light. As a simultaneous optical weight and delay, as well as a wavelength converter, a semiconductor optical amplifier operating in this manner can be a compact and versatile element in microwave photonics, radio-over-fiber, and general analog optical signal processing.

Comprehensive Investigation Modeling For Semiconductor Optical Amplifier (SOA)

This paper presents the effects of the input signal on the gain and carrier density response of a semiconductor optical amplifier (SOA). The SOA is modeled using a segmentation method. The input bias current, input power, wavelength and the length of SOA required for amplification and switching functions are investigated. Moreover, the effect of the temperature on SOA operation is investigated as well as the thermo-optical effect. The operation principle is simulated and the results show the input boundary conditions and requirements in which the SOA can be used as an amplifier and as switch.

Enhanced performance of semiconductor optical amplifier at high direct modulation speed with birefringent fiber loop

We employ a birefringent fiber loop (BFL) for enhancing the performance of a semiconductor optical amplifier (SOA) which is directly modulated. By properly exploiting the BFL comb-like spectral response, we show that the SOA can be directly modulated at a data rate which is more than five times faster than that enabled by the SOA electrical bandwidth. The experimental results, which include chirp measurements, demonstrate the significant improvements achieved in the performance of the directly modulated SOA with the help of the BFL.

Semiconductor optical amplifier pattern effect suppression with passive single microring resonator-based notch filter

We propose to employ a passive single microring resonator (MRR) to suppress the pattern effect in a semiconductor optical amplifier (SOA). We specify the necessary conditions that must hold in order for the MRR to act as notch filter and compensate for the uneven spectral broadening of the amplified data pulses. This procedure allows us to find the permissible range of values of the MRR radius and suitably select this parameter so that the defined design criteria are satisfied and the employed figure-of-merits are acceptable. If designed and constructed as suggested, which is feasible with state-of-the-art technology, the MRR-based notch filter enables to significantly improve the pattern-dependent SOA performance and the quality characteristics of the amplified signal.

Optimization of Intensity Noise Reduction from an Incoherent Light Source Using Gain Saturated Semiconductor Optical Amplifier in a Spectrum-sliced Channel at 2.5 Gb\\S

The “spectrum-slicing” technique employing incoherent light has been shown to be a highly practical, cheap and hence very attractive proposal for future all-optical networks. In this study, the use of Semiconductor Optical Amplifier (SOA) gain saturation for intensity noise reduction of incoherent light is studied with a view to obtaining the optimum SOA injection current and input power conditions to achieve the best possible intensity noise reduction-in terms of OSNR, BER, noise power and Q-factor. The results reported herein give designers knowledge of the best SOA operating conditions to enhance overall system performance, while still obtaining signal gain from the SOA.

Wide Locking Range and Multi-Channel Clock Recovery Using a Silicon Microring Resonator

An all-optical clock recovery (CR) scheme with wide locking range is demonstrated, based on a silicon microring resonator (MRR) and a semiconductor optical amplifier (SOA). The MRR with a free spectral range of 40 GHz works as a comb filter, which removes the modulation information, whereas the SOA operating in the saturation regime performs amplitude equalization to achieve a good optical clock signal. The design of the MRR is investigated according to the tolerance of the subsequent equalizer. Based on the fabricated MRR, single and dual channels CR from 40 Gb/s input data streams can be achieved successfully with root mean square time jitter of ~ 900 fs. Because of the moderate finesse of the MRR, the CR can be achieved with a wide range of several gigahertz.

Quantifying system performance improvements in a high-density spectrum-sliced channel running at 10 Gb/s using semiconductor optical amplifier gain compression nonlinearities

We report on the use of semiconductor optical amplifier (SOA) gain compression for achieving intensity noise reduction in light from an incoherent broadband source, running at high data rate of 10 Gb/s in a narrow spectrum-sliced high-intensity channel of 20 GHz (∼0.16 nm ) bandwidth, in order to improve quality of performance in future spectrum-sliced systems. Data have been collected on the performance of a single SOA as noise reducer at various input powers and biases. Improvements of ∼20 dB in the relative intensity noise, together with commensurate improvements in both signal-to-noise ratio and quality factor, have been achieved at a nominal 0 dBm of power inserted into the SOA at 0.15 A bias. The overall results obtained herein give designers a knowledge of the best SOA operating conditions required, particularly in terms of bias and input power, in order to achieve a desired intensity noise reduction, and thus an overall system performance improvement, while still obtaining some signal gain from the SOA as well.

Swept-Source OCT System Based on a Polarization-Dependent Semiconductor Optical Amplifier-Enabled Fourier Domain Mode Locked Laser

We demonstrate a swept-source OCT system based on a polorization-dependent semiconductor optical amplifier (SOA)-enabled Fourier Domain Mode Locked laser (FDML). The broad bandwidth and high saturation power of the semiconductor optical amplifier enables single semiconductor optical amplifier operation with enough bandwidth and output power. The FDML generates ~32mW output power at 45kHz sweep rates, with a tuning range of 115 nm centered at 1326 nm. Using the SOA-enabled FDML laser, ~12.9μm axial resolution,9μm transverse spot size and 105dB sensitivity are achieved. OCT imaging of biological sample is also demonstrated.

New simulative studies on performance of semiconductor optical amplifier based optical switches like frequency converter and add-drop multiplexer for optical data processors

Optics has proved its successful role in parallel logic, arithmetic or algebraic operations. So many different methods on optical data processing were proposed and implemented in last few decades. For implementing the all optical logic and arithmetic devices it needs different types of encoding principle like, polarization encoding principle, frequency encoding principle, intensity encoding principle and phase encoding principle. As the frequency is the basic characteristics of light, so frequency encoding principle is the most reliable one among all other encoding principles. Currently frequency encoding technique is established as a promising one for all optical processing, as frequency of light does not change normally after reflection, refraction, absorption etc. Again Semiconductor optical amplifier (SOA) can be used for different successful frequency conversions. Here in this technique ‘1’ logic state is represented by a frequency ν2 then ‘0’ state is represented by another frequency ν1 instead of intensity variation. In this paper the authors describe the simulation study of the performances of SOA in various optical switches like frequency conversion and add-drop multiplexer.

Quantum-dot semiconductor optical amplifier performance management under optical injection

The effect of an external beam on different characteristics of quantum-dot semiconductor optical amplifiers (QD-SOAs) has been investigated experimentally. It has been shown that injection of a relatively weak light beam at the gain transparency wavelength accelerates the full gain recovery time from 80 ps to 65 ps while it increases the saturation output power (SOP) by more than 2 dB if the beam resides in the gain region. The effect of the external beam on the fiber-to-fiber gain has been demonstrated at both the gain transparency wavelength and close to gain peak wavelength. These results are expected to be further enhanced by increasing the injected beam power, which has a peak value of ∼7 mW in the experiments.

Optimised non-uniform biasing technique for a high-speed optical router to achieve uniform semiconductor optical amplifier gain

In this study, we propose applying non-uniform biasing current technique to improve the gain uniformity of the semiconductor optical amplifier (SOA) for high-speed optical routers. The output pulses will have high-gain deviation because of the high-speed input pulses and the slow SOA gain recovery, thus resulting in a high system power penalty. The theoretical SOA operation principle is demonstrated using a segmentation model that employs the rate and propagation equations with third-order gain coefficients. The impact of the bias current on the SOA gain responses owing to the input packet of 1 mW input Gaussian pulses at a wavelength of 1550 nm is analysed in order to optimise the proposed non-uniform bias current shape. The uniform and the optimised non-uniform bias current techniques are investigated in terms of the SOA gain uniformity and the average output power for high-speed data rates from 10 to 160 Gb/s. The impact of the average bias current applied to the SOA on the non-uniform shape is also investigated at all input data rates. Results obtained show a significant improvement in the gain standard deviation of 4.6, 6.3, 8.7, 10.1 and 10.2 dB for the data rates of 10, 20, 40, 80 and 160 Gb/s, respectively, when applying 150 mA average non-uniform biasing and these values reaches 15.2, 16.3, 17.7, 18 and 17.4 dB at 200 mA. The proposed technique also offers an increase in the average output power for the input pulses compared with uniform biasing.