The paper reviews the current status and designs of all-optical gates. Various schemes with and without semiconductor optical amplifiers are discussed and compared. The optical gates are classified according to their design structures. It is divided into two major divisions that is, nonsemiconductor optical amplifier based gates and semiconductor optical amplifier based gates. In nonsemiconductor optical amplifier based gates, different schemes have been proposed to create non-linearity which is discussed. The semiconductor optical amplifier based gates of different design structures are discussed to show the probe pulse that is modulated in different ways to obtain results.

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All-Optical Logic Gates: Designs, Classification, and Comparison

Suppressing the intrinsic imaginary interference (IMI) effect induced by the multiple-path fading channel is the key technology for maintaining the good performance of the orthogonal frequency-division multiplexing offset-quadrature amplitude modulation (OFDM/OQAM) systems. Recently, the first theoretical discussion on the IMI effect and the corresponding frequency-domain channel estimation method for polarization-division-multiplexed (PDM) coherent optical OFDM/OQAM (CO-OFDM/OQAM) system has been studied. The full-loaded and the half-loaded channel estimation methods have been proposed to mitigate the IMI effect. However, for these frequency-domain methods, the condition that the symbol interval is much longer than the maximum channel delay spread has to be satisfied. When the transmission distance is long, the frequency-domain residual errors induced by the chromatic dispersion (CD) and polarization mode dispersion (PMD) reduce the channel estimation accuracy evidently. In this paper, we systematically discuss the time-domain channel transmission model for PDM CO-OFDM/OQAM systems. With the analysis of the distribution of the received additive noise, we propose the time-domain least square (TDLS) channel estimation method for PDM CO-OFDM/OQAM systems. Compared with the frequency-domain methods, the TDLS method promotes the system robustness against both the IMI effect and the additive noise significantly. The computational complexities and the transmission performance have been compared for both the TDLS and the frequency-domain full-loaded methods. The theoretical analysis is validated by numerical Monte Carlo simulations of the PDM CO-OFDM/OQAM system.

Time-Domain Least Square Channel Estimation for Polarization-Division-Multiplexed CO-OFDM/OQAM Systems

The feasibility of implementing reconfigurable ultrafast all-optical NOR and NAND gates by employing a single Mach–Zehnder interferometer (MZI) with quantum-dot semiconductor optical amplifiers (QD-SOAs) is theoretically investigated. The reconfiguration of the scheme that allows conversion from one gate to the other is achieved by simply turning on or off a clock signal, while the complement of one of the data signals is used too as input for both gates. By conducting a numerical simulation, the conditions under which the QD-SOA-based MZI must be adjusted to operate so as to simultaneously ensure an acceptable extinction ratio for the NOR and amplitude modulation for the NAND are specified. This procedure is more demanding than when each gate is considered separately. Nevertheless it is possible to extract technologically realistic and achievable guidelines for the data signals and QD-SOAs characteristics in order for these gates to be jointly designed without modifying the fundamental structure or data driving mode of the MZI switch. In this manner a permissible range and a proper selection of values for the critical performance parameters that is common for these universal logic gates is derived, which enables both of them to be realized with a logically correct and high quality outcome.

https://iopscience.iop.org/article/10.1088/2040-8978/14/10/105401/pdf

On the design of reconfigurable ultrafast all-optical NOR and NAND gates using a single quantum-dot semiconductor optical amplifier-based Mach–Zehnder interferometer

A reconfigurable dual-channel all-optical logic gate is proposed and experimentally demonstrated using four-wave mixing in a silicon waveguide for polarization encoding signals Six logic functions, XNOR, AND, NOR, XOR, AB¯, and A¯B are implemented at two different wavelength channels by adjusting the polarization states of two 10 Gb/s non-return-to-zero polarization-shift keying (NRZ-PolSK) signals modulated by 10-bit on–off keying (OOK) sequences The eye diagrams of the logic signals are clearly observed, and the logic functions are well demonstrated as the two incident NRZ-PolSK signals are both modulated by the OOK sequences, which originate from 231−1 pseudo-random binary sequences

Reconfigurable dual-channel all-optical logic gate in a silicon waveguide using polarization encoding.

An all-optical AND logic gate in a single silicon microring resonator is experimentally demonstrated at 10 Gb/s with 50% RZ-OOK signals. By setting the wavelengths of two intensity-modulated input pumps on the resonances of the microring resonator, field-enhanced four-wave mixing with a total input power of only 8.5 dBm takes place in the ring, resulting in the generation of an idler whose intensity follows the logic operation between the pumps. Clear and open eye diagrams with a bit-error- ratio below 10−9 are achieved.

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All-optical 10 Gb/s AND logic gate in a silicon microring resonator

Reconfigurable all-optical logic gate using four-wave mixing (FWM) in HNLF for NRZ-PolSK signal

We demonstrate a reconfigurable all-optical logic gate for NRZ-PolSK signal based on FWM in a highly nonlinear fibe at 10Gb/s. Half-subtracter, XOR, AB, AB or XNOR, AND, NOR logic gates can be implemented simultaneously. Power penalties are less than 3dB.

Reconfigurable and simultaneous implementation of all-optical logic gate using four-wave mixing (FWM) in HNLF for NRZ-olSK signal

We propose and demonstrate an in-band optical signal-to-noise ratio (OSNR) monitoring technique using the output power ratio (PR) of the nonlinear optical loop mirror (NOLM) theoretically and experimentally. Operation point (OP) is investigated to be the input average power which corresponds to the first maximum of the power ratio curve. The monitoring performances using PR are proved to be better than those just using one output port of NOLM for on-off keying (OOK) and differential phase-shift-keying (DPSK) signals with different duty cycles: non-return-to-zero (NRZ), carrier-suppressed return-to zero (CSRZ), return-to-zero (RZ) with 50% and 33% duty cycle (RZ 50 and RZ 33) at 40 Gb/s. For 80 Gb/s RZ-differential quadrature phase-shift keying (DQPSK) signal, we obtained 12.16 dB maximum power variation and 13-39.8 dB monitoring range experimentally. The power ratio scheme can improve the contrast ratio by 7.05 dB and the monitoring range by 13.8 dB compared with that just using the transmission port. The tolerance to residual chromatic dispersion of the monitoring performance is investigated to be less than 1.7 ps/nm. The experimental validations are consistent with the theoretical analyses. The proposed scheme can be used in ultra-speed transmission systems.

Investigation of In-Band OSNR Monitoring Technique Using Power Ratio

The invention discloses an optical signal to noise ratio (OSNR) monitoring device and monitoring method, comprising an optical amplifier (1), a first polarization control element (2), a circulator (3), a coupler (4), a nonlinear optical element (5), an attenuator (6), a second polarization control element (7), a first power meter (8) and a second power meter (9). The invention further discloses an OSNR monitoring method using the device, comprising the following steps: optimizing the polarization control elements to obtain working conditions of the linear area of the device; describing the power transmittance ratio of a transmission end to a reflection end of the monitoring device; fitting the relation between an OSNR and an output power by using a least square method; and back-calculating the OSNR by the output power according to the relation. The device and method disclosed by the invention are suitable for high-speed optical communication system. The device and method are compared with the prior scheme, the flexibility and monitoring range are improved obviously.

Lanlan Li

Papers

Reconfigurable all-optical logic gate using four-wave mixing (FWM) in HNLF for NRZ-PolSK signal

Reconfigurable and simultaneous implementation of all-optical logic gate using four-wave mixing (FWM) in HNLF for NRZ-olSK signal

Investigation of In-Band OSNR Monitoring Technique Using Power Ratio

Optical signal to noise ratio (OSNR) monitoring device and monitoring method

Investigation of a simultaneous multifunctional photonic logic gate based on bidirectional FWM