10 Gbit/s all-optical non-return to zero-return-to-zero data format conversion based on a backward dark-optical-comb injected semiconductor optical amplifier

By using a semiconductor optical amplifier backward injected by a dark-optical-comb pulse train at 10 GHz, we demonstrate a 10 Gbit/s all-optical nonreturn-to-zero (NRZ) to return-to-zero (RZ) format conversion of an incoming optical pseudorandom binary sequence (PRBS) data stream. Both the polarity and the wavelength of data are conserved during format conversion. Without any pre-amplification, the extinction ratio of degraded optical NRZ PRBS data is greatly improved from 7.13 to 13.6 dB after NRZ-to-RZ conversion. An ultralow bit-error rate of 10(-12) at a data rate as high as 10 Gbits/s is obtained with a received optical power of -18.3 dBm. The converted RZ PRBS data exhibit a negative power penalty of >3.7 dB compared with the NRZ PRBS data at a bit-error rate of 10(-12).     

Signal Demultiplexing from an 8.2×2.5 Gb/s OTDM Data Stream Using NOLM: Demonstration and Bit Error Rate Measurement

It is presented the experiment of all-optical demultiplexing of one 2.5 Gb/s channel from an 8×2.5 Gb/s OTDM data stream using nonlinear optical loop morror with 3 km dispersion shifted fiber. Bit error rate (BER) of the demultiplexed channel is measured. A BER of 10-11 is achieved and the power penalty is only 1.4 dB when BER is 10-9.     

采用QPSK调制的50 Gbit/s高速大气激光通信传输特性研究

高级多电平调制格式在海上高速和高光谱效率的光通信中已经显示出巨大的潜力。将正交相移键控(QPSK)调制格式引入自由空间光(FSO)通信,实验证明可实现高达50 Gbit/s的高速FSO传输链路,能够清楚地观察到所发送的QPSK信号的眼图和星座图。通过比较传输之前和之后的误码率曲线,可以发现接收灵敏度都小于-36.7 dBm。当误码率为3.8×10-3时,它们的功率损失都小于4.2 dB。     

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 fiber at 10 Gb/s. Half subtracter, XOR, AB?, āB or XNOR, AND, and NOR logic gates can be implemented simultaneously. The input power for the HNLF is optimized to be as low as about 15.2 dBm and the high Q factors above 8 dB for eye diagrams are achieved. Experimental results show Q factors of AB?, āB, AND, and NOR were higher than those of XOR, and XNOR. Error-free operation is achieved experimentally for 10 Gb/s 2⁷-1 pseudorandom bit sequence (PRBS) data. Power penalties for the logic gate are less than 3 dB. Simulation analysis about the wavelength characteristic for all logic gates is given and it predicts that the reconfigurable logic gate can realize error-free operation when the wavelength separation is less than 5 nm.     

All-Optical RZ to NRZ Format Conversion Using Single SOA Assisted by Optical Band-Pass Filter

We propose a novel all-optical format conversion from the return-to-zero （RZ） to the non-return-to-zero （NRZ） based on single semiconductor optical amplifier （SOA） and optical band-pass filter （OBE）. We demonstrate the proof of the principle experiment at 10 Gbps by using the test SOA and OBF converter. The format conversion can be achieved with output extinction ratio of 11.51 dB. The BER is 5.5×10^-9 when the power of NRZ is - 10 dBm. The proposed scheme is robust and potential for applications in optical networks.     

Performance enhancement of the power penalty in DWDM FSO communication using DPPM and OOK modulation

This paper presents the design and performance enhancement of the power penalty (PP) in a dense wavelength division multiplexing based on free space optical communication (FSOC) link using digital pulse position modulation (DPPM) and on–off keying (OOK) modulation. Such a system has a high performance, low cost, robust and power efficient, reliable, excessive flexibility, and higher data rate for access networks. The system performance is evaluated for an 8-channel wavelength-division-multiplexing for hybrid fiber FSOC system at 2.5 Gbps on widely accepted modulation schemes under various atmospheric turbulence (AT) regimes conditions. The performance of system is introduced in terms of PP, bit-error rate (BER), transmission distance and the average received optical power. The numerical results shows that the improvement of the PP using DPPM modulation of 0.2–3.0 dB for weak turbulence (WT) regimes for BER of 10^?6 and above 20, 25 dB for strong turbulence (ST) regimes are reported for BER of 10^?6 and 10^?9, as respectively (depending on the AT level). Further, we develop of improvement the PP caused by multiple-access interference about 6.686 dB which is predicted for target BER of 10^?9 in WT and 1 dB at target BER of 10^?6 in ST when the 8 user are active on the system of optical network units. Additionally, the optical power budget and margin losses of a system are calculated with different link length. The proposed approach of DPPM merges superiority with higher enhancement of PP about 0.8 dB for BER equal 10^?9 at FSO link length l_fso?=?2000 m compared to OOK at 1 dB for WT. An improvement of 2 dB is observed using the DPPM scheme over an OOK due to capability of detect pulses under background noise conditions with increased receiver sensitivity.     

Multichannel dispersion compensation using a silicon waveguide-based optical phase conjugator

We experimentally demonstrate dispersion compensation using a silicon-based optical phase conjugator. We achieve simultaneous transmission of four dense wavelength division multiplexing (DWDM) channels spaced at 100 GHz and operating at 10 Gbits/s over 320 km of standard fiber. The measured power penalty at bit error rate of 10(-9) is less than 0.3 dB.     

All-optical multiple-channel logic XOR gate for NRZ-DPSK signals based on nondegenerate four-wave mixing in a silicon waveguide

We report an all-optical multiple-channel exclusive OR (XOR) gate for 10?Gbits/s non-return-to-zero differential phase-shift keying (NRZ-DPSK) signals using nondegenerate four-wave mixing in a silicon waveguide. The function of the logic XOR gate is experimentally demonstrated using 40?bit DPSK sequences. Also, the eye diagram of the XOR signal is clearly observed as the incident signals are both modulated by DPSK sequences originating from 2(31)-1 pseudorandom binary sequences.     

Frequency-swept coherently detected spectral amplitude code for flexible implicit optical label switching

A new optical label switching system with coherently detected implicit spectral amplitude code (SAC) labels is proposed in this letter. The implicit SAC labels are recognized using a frequency-swept local light source oscillator. Intensity modulation payloads of 625 Mb/s and 1.25 Gb/s are considered. Label and payload bit error rate (BER) performances are assessed and compared by simulations. The results reveal that, at a BER value of 10 9 , 32.4-dBm label received power can be obtained. In addition, 8.3-dB optical signal-to-noise ratio (OSNR) is obtained when carrying a payload of 625 Mb/s. The label BER value hardly reaches 10 -9 if the payload bit rate is at 1.25 Gb/s; however, a high payload bit rate only has little influence on received payload quality at a BER value of 10 -9 . Finally, a payload of 1.25 Gb/s could obtain 28.2 dBm received power and 9.5-dB OSNR.     

Bit error rate improvement by nonlinear optical decision element

We present a novel approach to the improvement of the bit error rate (BER) in optical communications. We propose a design of advanced optical receiver enhanced by a nonlinear all-optical decision element. As a particular example, we demonstrate a substantial improvement in the BER over the conventional receiver for operation at 40 Gbits/s.     

Silicon photonic crystal all-optical logic gates

All-optical logic gates, including OR, XOR, NOT, XNOR, and NAND gates, are realized theoretically in a two-dimensional silicon photonic crystal using the light beam interference effect. The ingenious photonic crystal waveguide component design, the precisely controlled optical path difference, and the elaborate device configuration ensure the simultaneous realization of five types of logic gate with low-power and a contrast ratio between the logic states of “1” and “0” as high as 20 dB. High power is not necessary for operation of these logic gate devices. This offers a simple and effective approach for the realization of integrated all-optical logic devices.     

All-optical simultaneous drop and wavelength conversion of DPSK data

We demonstrate an all-optical scheme for the simultaneous drop and wavelength conversion of bursts of data from a continuous stream of differential phase-shift keyed (DPSK) signals. This function is obtained in a single semiconductor optical amplifier Mach-Zehnder interferometer thanks to proper nonlinear interaction of the data stream and an optical gate signal at different wavelength. Fast switching-time enabling wavelength shifting operation on continuous DPSK data stream at 10 and 40 Gb/s without any bit loss is reported. Corresponding measured power penalties are negligible at 10 Gb/s and about 1.7 dB at 40 Gb/s.     

Designs of all-optical NOR gates using SOA based MZI

The paper investigates the non-linear behavior of semiconductor optical amplifier with Mach–Zehnder interferometer (SOA-MZI) configuration which makes it to work as a logic gate. The two designs of NOR gate based on SOA-MZI have been verified. The basic principal of both designs are same. The summation of data pulses have been taken and inverted to perform a NOR operation. In the design, the first 3 dB coupler creates a phase difference of π/2 in clock pulse and data pulse while passing through two interferometer arms. The clock and data pulses pass through SOA which attenuates the clock pulse wherever the data pulse is present. After passing through second 3 dB coupler a phase difference of π/2 is again created. Therefore, if the clock pulse is in the same phase will be added and if it is out of phase, will be canceled. The designs have been investigated at different bit-rates to achieve higher extinction ratio (ER), Q-factor and bit-error rate (BER) for different pump currents of SOA.     

All-optical circular shift register based on semiconductor optical amplifiers

We present a new and potentially integrable scheme to realize an all-optical circulating shift register consisting of a fiber-loop based optical buffer (OB) and an optical AND gate. The OB is implemented using semiconductor optical amplifier as a nonlinear element and the AND gate is realized by means of four wave mixing effect in a semiconductor optical amplifier. The operation of the shift register has been verified for a 10-bit input sequence at a sequence bit rate of 2.5 GHz and 10 GHz respectively. The simulation results show that \(\hbox {BER}=10^{-9}\) is achieved at optical signal-to-noise (OSNR) ratio of 16dB at the shift register output. The dependence of the output quality factor ( \(Q\) -factor) on SOA parameters is also investigated and discussed.     

AWG-based WDM-PON monitoring system using an optical switch and a WDM filter

A new WDM-PON scheme with real-time monitoring based on a time-sharing method is proposed. It uses an optical time domain reflectometer (OTDR) to monitor multiple ports by integrating an optical switch (OSW) with a dense wavelength division multiplexer (DWDM) at the optical line terminal (OLT) site. Each downstream signal and its corresponding monitoring signal are separated by m times the free-space range (FSR) of an array waveguide grating (AWG). A bit error rate (BER) test in 2.5 Gb/s × 27 km is performed with and without turning on the OTDR. A small power penalty of 0.7 dB is observed compared to the back-to-back measurement.     

用光脉冲注入从锁模激光二极管再生低抖动高Q值光时钟

采用１０ＧＨＺ基准时钟光和１０Ｇｂｉｔ／ｓ的数据脉冲信号光注入到锁模激光二极管，降低了周期抖动，当注入功率为－５ｄＢｍ，在基准时钟光波长等于锁模激光二极管的光波长时，获得的最小抖动为０．２５ｐｓ，采用给锁模激光二极管，在注入功率为＋２７ｄＢｍ时，其Ｑ值达３０００。     

All-optical extinction-ratio enhancement of a 160 GHz pulse train by a saturable-absorber vertical microcavity

A vertical-access passive all-optical gate has been used to improve the extinction ratio of a 160 GHz pico-second pulse train at 1555 nm. An extinction ratio enhancement of 6 dB is observed within an 8 nm bandwidth. Such a device is a promising candidate for low-cost all optical reamplication and reshaping (2R) regeneration at 160 Gbits/s.     

High Quality Factor Q and Low Timing Jitter from MLLD Using Optical Injection

采用１０ＧＨｚ基准时钟光和１０Ｇｂｉｔ／ｓ的数据脉冲信号光注入到锁模激光二极管，降低了周期抖动，当注入功率为－５ｄＢｍ，在基准时钟光波长等于锁模激光二极管的光波长时，获得的最小抖动为０．２５ｐｓ，采用混合锁模激光二极管，在注入功率为＋２７ｄＢｍ时，其Ｑ值达３０００．     

基于压扩变换的60GHz正交频分复用光载无线通信系统实验研究

提出并实验研究了在60GHz正交频分复用(OFDM)-光载无线通信(ROF)系统中采用压扩变换技术降低OFDM信号峰值平均功率比(PAPR),并提高系统的接收灵敏度。实验结果表明,携带基于压扩变换的2.5Gb/s60GHz的OFDM-ROF信号经标准单模光纤传输50km后,在无色散补偿和误码率为10-3的条件下,当入纤功率为12dBm时,系统接收灵敏度提高约2.3dB,并且当互补累积分布函数(CCDF)为10-4时,OFDM信号的PAPR下降约3dB。     

Performance limitations of an optical heterodyne CPFSK transmission system due to self-phase modulation

A detailed theoretical analysis is presented to evaluate the combined influence of self-phase modulation (SPM) and group velocity dispersion (GVD) of optical fiber on the bit error rate (BER) performance of a heterodyne optical CPFSK system. The power penalty suffered by the system due to the combined influence of GVD and SPM is evaluated from the BER performance results. It is found that the penalty due to SPM at a BER of 10⁻⁹ is significant when the input power exceeds 7 dBm. Further, the CPFSK system with modulation index of 0.5 is less sensitive to the effects of GVD and SPM compared to the system with a modulation index of 1. The theoretical results are in conformity with the experimental results reported earlier.