Cross-gain Modulation Research Articles

Optically Controlled RF Phase Shifts in SOAs by Adding the XGM Response of an Optical Signal

This study focuses on the possibility to achieve optical control of the radiofrequency (RF) phase shifting in semiconductor optical amplifiers (SOA). Based on the addition of the cross-gain modulation response (XGM) of a CW signal at an SOA output, the phase shift can be independently controlled from the operating conditions of the SOA (optical input power and bias current) by varying the external CW power. The impact of the XGM response of the amplified spontaneous emission (ASE) on the signal relative phase shift has also been studied. Small-signal analysis is developed and a numerical calculation is used to analyze the controllable RF phase shift. The measurement results for several control signal powers are given.

Lossless WDM PON Photonic Integrated Receivers Including SOAs

The role of a semiconductor optical amplifier (SOA) for amplifying downstream traffic at optical network terminals (ONT) within a silicon-photonics integrated receiver in a high capacity passive optical network (PON) is investigated. The nearly traveling wave SOA effects are evaluated by considering fabrication and link loss constraints through numerical analysis and experimental validation. The impact of hybrid integration of a SOA chip on a silicon on insulator (SOI) photonic chip using the flip chip bonding technique on SOA design is evaluated through numerical analysis of a multi section cavity model. The performance of the proposed ONT receiver design employing twin parallel SOAs is evaluated experimentally on a 32 × 25 Gb/s OOK WDM transmission system considering cross gain modulation (XGM) and amplified spontaneous emission (ASE) constraints. The XGM impact is evaluated through 32 channel wavelength division multiplexing (WDM) transmission and a likely PON worst case scenario of high channel power difference (~10 dB) between adjacent channels. The impact of ASE is evaluated through the worst-case polarization condition, i.e., when all of the signal is coupled to only one. Successful transmission was achieved in both worst-case conditions with limited impact on performance. SOA results indicate that a maximum residual facet reflectivity of 4 × 10−4 for the chip-bonded device can lead to a power penalty below 2 dB in a polarization-diversity twin SOAs receiver.

On-Chip All-Optical Wavelength Conversion of PAM-4 Signals Using an Integrated SOA-Based Turbo-Switch Circuit

We experimentally demonstrate on-chip all-optical wavelength conversion (AOWC) of four-level pulse amplitude modulation (PAM-4) signals by cross-gain modulation in an InP monolithically integrated turbo-switch circuit based on semiconductor optical amplifiers (SOAs). Full characterization of the photonic integrated circuit (PIC) is given, where sevenfold reduction in effective gain recovery is achieved by the PIC turbo-switch compared with a case of single SOA switch. Wavelength conversion of 25 Gbit/s PAM-4 signal in the C-band is successfully demonstrated with ~2 dB power penalty at 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> bit error rate. Moreover, the wavelength dependence of the converter is studied. The integrated AOWC device has the advantages of high-speed switching operation as well as small footprint, high stability, and low switching power.

A novel model of all-optical reversible XOR/XNOR logic gate on a single photonic circuit

The high speed and high volume of optical data are subjected to electronic conversions at the receiving end of the optical network for processing purposes. This optoelectronic conversion makes the system inefficient in terms of speed and bandwidth. When high-speed data are subjected to electronic processing, heat dissipates from electronic circuits. Another source of heat dissipation is the loss of information from the irreversible processors. The solution of this problem is reversible computing. This research paper proposes a novel 3 × 3 reversible XOR logic gate and XNOR logic gate in a single photonic circuit. The proposed photonic circuit works on the principles of cross-gain modulation and cross-phase modulation, which is introduced by the active regions of two semiconductor optical amplifier in a Mach–Zehnder interferometer structure. The proposed design works at 10 Gbps data rate. The average extinction ratio of the design is 18.58 dB, and the average quality factor is 63.03 dB. The optical cost of the proposed circuit is 1 unit.

基于交叉增益调制的集成全光可编程逻辑阵列研究

基于交叉增益调制的集成全光可编程逻辑阵列研究

All-optical reconfigurable non-inverted logic gates with a single semiconductor optical amplifier

All-optical reconfigurable non-inverted logic gates with a single semiconductor optical amplifier (SOA) is proposed. Compared with the probe light of continuous light, the clock (Clk) pulse sequences light is regarded as the probe light so that the output of logic gates is a non-inverted code which is suitable to the further combination of different logic gates. The scheme is based on a single SOA with four-wave mixing and cross-gain modulation. Multiple functional logic operations are implemented and switched by adjusting the center wavelength of tunable optical band-pass filter without altering the experimental device. In the experiment, all-optical multiple logic gates with 10 Gb/s return-to-zero of NOT, NOR, XNOR, AND, A¯•B and A•B¯ are realized. Meanwhile, because Clk probe light is a small signal, a saturable absorber (SA) is configured to improve the extinction ratio (ER) and optical signal to noise ratio (OSNR). For logic gates NOT, NOR and XNOR with Clk probe light, ER and OSNR are only deteriorated by 1 dB with the SA. For logic gate AND with Clk probe light, ER is improved by about 2 dB based on four-wave mixing and OSNR keep the original values with the SA respectively. For logic gates A¯•B and A•B¯ without Clk probe light, ER and OSNR are both only deteriorated by 0.5 dB. It has the potential to obtain more complex combinational logic gates.

Demonstration of All-Optical Logic Gate Device Using MQW-SOA and 10 Gbps XNOR Operation

All-optical logic gate device as a label recognition device for all optical packet networks, which is integrated with a multi-quantum-well semiconductor optical amplifier (MQW-SOA) and double micro-ring resonators (MRRs) is proposed. The nonlinearity of an MQW-SOA such as cross-gain modulation (XGM) and four-wave mixing (FWM) is investigated, and the operation conditions of the input powers and the wavelengths are clarified for efficient XGM and FWM operation. On the basis of these conditions, all-optical XNOR operation at 10 Gbps is demonstrated with clear eye opening

Modeling the effects of interband and intraband transitions on phase and gain stabilities of quantum dot semiconductor optical amplifiers

In this paper, the effects of interband and intraband transitions on the gain and phase stabilities in quantum dot semiconductor optical amplifier (QD-SOA) are investigated both temporally and spectrally employing electrical and optical pumping schemes. For this purpose, the carrier rate equations in different energy states coupled to the traveling wave optical field equation have been numerically solved to derive the dynamical behavior of QD-SOA. Our results show that the gain and phase response can be stabled under optical pumping (OP) scheme because the role of the interband and intraband transitions on the dynamics of QD-SOA is reduced. This behavior leads to high-speed pattern effect-free cross-phase modulation (XPM) in QD-SOA. It is found that optically pumped QD-SOA can have high performance in phase based applications. Moreover, it is shown that under OP scheme although the QD-SOA has lower gain value and slower gain recovery time, the ultrafast cross-gain modulation (XGM) without pattern effect is possible and the phase is recovered within a shorter time compared to EP scheme. The behavior arises from the different capacity of the carrier reservoir for pumping schemes.

Multichannel and Multistate All-Optical Switch Using Quantum-Dot and Sample-Grating Semiconductor Optical Amplifier

A novel type of multichannel and multistate all-optical switch using a single sample-grating quantum-dot-distributed feedback semiconductor optical amplifier has been proposed and theoretically demonstrated. The multichannel device, which operates below threshold, utilizes cross-gain modulation and the sample-grating technique. The multichannel outputs are strongly coupled and are utilized to get multistability at several wavelength channels. Three logic states can be obtained when the inputs are properly detuned to the sample-grating comb modes. The three logic states, which exhibit reasonable gain, are separated by wide hysteresis width and can be tuned to a different wavelength channels. The device characteristics are very useful for building all-optical logic gates, flip-flops, and decision circuits.

Applicability of a model with average inversion level to a cladding-pumped multicore erbium-doped fiber amplifier

This paper investigates the applicability of a model of a cladding-pumped multicore erbium-doped fiber amplifier (CP-MC-EDFA) that employs the average inversion level of an erbium ion. The model is modified to include the effects of multiple cores for modifications of the background loss coefficient of the pump light. The model is validated experimentally by measurements of the pump power, gain transient, and intercore cross-gain modulation of a cladding-pumped 12-core EDFA in which the pump light is uniformly distributed in the inner cladding. The calculated and measured pump power, gain transient response, and gain change caused by the intercore cross-gain modulation agree well, suggesting the modified model is useful for characterizing a CP-MC-EDFA.

Carrier-Envelope Offset Frequency Stabilization of a Fiber Laser by Cross Gain Modulation

We present the first carrier-envelope offset (CEO) frequency stabilization of a fiber laser by cross gain modulation. The Yb-doped fiber laser is mode-locked by nonlinear polarization evolution and emits 32-nm wide dissipative solitons at a repetition rate of 125 MHz with 150 mW of average output power. A continuous wave laser signal at a wavelength of 1025 nm is used as an intracavity power modulator. A low power of only 200 μW of modulator signal is coupled into the fiber laser and amplified in the gain segment. This signal cross modulates the laser gain, achieving 40 times larger modulation bandwidth of the intracavity laser power than with standard pump-current control. A tight CEO lock is demonstrated with 361 mrad of residual integrated phase noise (from 1 Hz to 1 MHz). The method allows easy implementation in many existing fiber laser frequency combs based on various saturable absorbers and fiber configurations.

Performance analysis of different designs of all-optical D flip flop

All optical flip flops play an important role in optical networks as well as in the field of optical computing. Optical memories are used for storing decisions in photonic packet routers temporarily. In this paper all optical D-flip flop is designed based on all optical gates. The nonlinear effects such as XGM (Cross Gain Modulation), XPM (Cross Phase Modulation) and FWM (Four Wave Mixing) are used to design all optical gates. We designed the D flip flop based on two logic that are NAND-NAND logic and NAND-NOR logic. The performance of both the designs is analyzed and the functionality of all optical D-flip-flop is verified using the truth table. It is proved that NAND-NAND logic is more effective than NAND-NOR logic.

Wavelength Conversion of 25-Gbit/s PAM-4 Signals Using a Quantum-Dot SOA

We demonstrate all-optical wavelength conversion of a 4-level pulse-amplitude modulation (PAM-4) signal by cross gain modulation (XGM) in a quantum-dot semiconductor optical amplifier (QD-SOA). In this scheme, the center passband of a conventional optical filter located at the QD-SOA output is slightly shifted to the shorter wavelength side [blue-shifted filtering (BSF)], which enables us to accelerate the gain recovery time of the QD-SOA and reduce the bandwidth limitation in the process of the wavelength conversion. By using the combination of XGM and BSF, we successfully achieve 25-Gbit/s PAM-4 wavelength conversion, with good conversion performance in terms of error-vector magnitude. We also investigate the conversion performance in a wide wavelength-hopping range and the high tolerance to the shift in input signal wavelength for use in data center applications.

Width-tunable pulse laser via optical injection induced gain modulation of semiconductor optical amplifiers

A width-tunable pulse laser via an optical injection induced gain modulation of a semiconductor optical amplifier (SOA) is demonstrated. When the pump current of the SOA is 330 mA or 400 mA and a continuous wave is injected into the laser cavity with different powers, bright or dark pulses with different pulse widths and frequency repetition rates are obtained. The bright and dark pulses are formed by the effect of gain dispersion and cross-gain modulation of the SOA.

All-optical multistability using cross-gain modulation in quantum-dot distributed feedback semiconductor optical amplifier

We propose and theoretically demonstrate a novel type of all-optical multistable device using single quantum dot distributed feedback semiconductor optical amplifier. The device utilizes cross-gain modulation with proper wavelength detuning to obtain multistability in a conventional DFB semiconductor optical amplifier. We find that dual bistability, which can be adjusted vertically or horizontally by applying small probe input, can be obtained in both the pump and the probe characteristics. Adjustable switching with contrast ratio as high as 14 dB is obtained from the probe signal.

Research on a scheme of generating ultra-wideband doublet signal based on the cross-gain modulation in a semiconductor optical amplifier

Research on a scheme of generating ultra-wideband doublet signal based on the cross-gain modulation in a semiconductor optical amplifier

A simultaneous all-optical half/full-subtraction strategy using cascaded highly nonlinear fibers

Using non-linear effects such as cross-gain modulation (XGM) and cross-phase modulation (XPM) inside two highly non-linear fibres (HNLF) arranged in cascaded configuration, a simultaneous half/full-subtracter is proposed. The proposed simultaneous half/full-subtracter design is attractive due to several features such as input data pattern independence and usage of minimal number of non-linear elements i.e. HNLFs. Proof of concept simulations have been conducted at 100 Gbps rate, indicating fine performance, as extinction ratio (dB) > 6.28 dB and eye opening factors (EO) > 77.1072% are recorded for each implemented output. The proposed simultaneous half/full-subtracter can be used as a key component in all-optical information processing circuits.

Calibrated Link Budget of a Silicon Photonics WDM Transceiver with SOA and Semiconductor Mode-Locked Laser

Based on the single channel characterization of a Silicon Photonics (SiP) transceiver with Semiconductor Optical Amplifier (SOA) and semiconductor Mode-Locked Laser (MLL), we evaluate the optical power budget of a corresponding Wavelength Division Multiplexed (WDM) link in which penalties associated to multi-channel operation and the management of polarization diversity are introduced. In particular, channel cross-talk as well as Cross Gain Modulation (XGM) and Four Wave Mixing (FWM) inside the SOA are taken into account. Based on these link budget models, the technology is expected to support up to 12 multiplexed channels without channel pre-emphasis or equalization. Forward Error Correction (FEC) does not appear to be required at 14 Gbps if the SOA is maintained at 25 °C and MLL-to-SiP as well as SiP-to-SOA interface losses can be maintained below 3 dB. In semi-cooled operation with an SOA temperature below 55 °C, multi-channel operation is expected to be compatible with standard 802.3bj Reed-Solomon FEC at 14 Gbps provided interface losses are maintained below 4.5 dB. With these interface losses and some improvements to the Transmitter (Tx) and Receiver (Rx) electronics, 25 Gbps multi-channel operation is expected to be compatible with 7% overhead hard decision FEC.

Optical Gain Depending on Both Size Fluctuations of Quantum Dots and Temperature in InGaAs/GaAs QD-SOA

On the basis of the coupled rate equations of the carriers in different energy states, the optical gain of an InGaAs/GaAs quantum dot (QD) semiconductor optical amplifier (QD-SOA) related to both the standard deviation of QD relative size fluctuation and the temperature is numerically investigated with a fourth-order Runge–Kutta method. Our results show that the quasi-flat gain spectra with the full-width at half-maximum more than 150 nm overlapped by the optical gains of both the ground state (GS) and the excited state (ES) can be achieved by either injection current density or temperature. When a pump light is resonant to the GS transition, the peak gain of the GS is not only varied with pump power, but the peak gain of the ES is also changed with this one. The ES may exhibit abnormal gain saturation at room temperature (300 K), which is considerably different from those of bulk and quantum-well SOAs. We predict that the QD-SOA both acting as an optical amplifier is applied to dense wavelength division multiplexing systems and acting as an all-optical wavelength converter implements the wavelength conversion without inverse codes based on the cross gain modulation.

Simple semi-analytical model for bistable cross-gain modulation in quantum dot VCSOAs

A novel semi-analytical model for cross-gain modulation (XGM) in quantum dot vertical-cavity semiconductor optical amplifier has been derived. The derived model, which is simple, requires small computational time compared with numerical simulation and can efficiently be used to investigate the optical bistable/stable characteristics of the device. Large XGM bandwidth can also be obtained when the device operates in the bistable region and in the stable region close to the bistable edge. A figure of merit is proposed to optimize the complicated tradeoff between the XGM bandwidth, efficiency, applied current and the input pump to probe ratio. We find that optimum characteristics can be obtained in our investigated device when the probe wavelength is detuned by 9 A above the resonant wavelength and when a specific CW probe density is applied to the input of the device.