All-optical wavelength conversion for 10-Gb/s NRZ payload and 2.5-Gb/s OFDM label in optical-packet-switched network

Simultaneous wavelength conversion based on four-wave mixing (FWM) for 10-Gb/s NRZ payload and 2.5-Gb/s OFDM label signals in optical switching network is experimentally demonstrated. The dual-pump scheme based on FWM in semiconductor optical amplifier (SOA) is employed and simultaneous wavelength conversion for optical packet with one optical payload of 10-Gb/s non-return-to-zero (NRZ) on-off keying (OOK) signals and one optical label of 2.5-Gb/s OFDM signals are realized. The bit-error-rate performance is evaluated for both payload and label after wavelength conversion.     

采用OFDM信号作为标记的光分组交换方案

以光正交频分复用信号作为光标记,利用两个不同波长的光载波分别经过强度调制,产生了10 Gb/sOOK光载荷和2.5 Gb/sOFDM光标记。测得了光分组信号经光纤传输前后接收载荷的眼图和标记的星座图以及误码率曲线,结果表明:经过40 km光纤传输后,载荷与标记的功率代价分别为1dB和0.5dB。     

Novel optical packet switching scheme using OFDM label with one core router and two edge routers

In this paper, we propose and experimentally demonstrate a novel optical packet switching scheme with one core router and two edge routers, in which an orthogonal frequency division multiplexing (OFDM) signal is generated as a label. In this experiment there are two transmission spans, each span consists of 50-km SMF-28 and an erbium-doped optical fiber amplifier (EDFA) without dispersion management. A 10 Gb/s on-off keying (OOK) optical payload and a 2.5 Gb/s OFDM optical label are generated, encapsulated, and transmitted in the first span. And then old label is replaced by new label, the generated new optical packet after transmission over the second span is detached and detected. The transmission performance of the optical label and payload is experimentally investigated at the ingress router, core router and egress router.     

Concurrent generation of an optical code label and payload data by use of phase and intensity modulators for all-optical packet switching

We propose and experimentally demonstrate the concurrent generation of an optical code label and payload data by use of off-the-shelf optical intensity and phase modulators in a tandem structure. This technique is capable of reconfigurable generation of an arbitrarily long optical code label of phase-shift keying concurrently with the generation of payload data, without the need for a special class of optical encoder. This technique will be powerful for all-optical packet switching networks, based on scalability and compactness, for optical code labels.     

Experimental demonstration and cascadability analysis of a tunable optical buffer based on a re-circulating loop consisting of optical SSB modulator and FBG filter

We demonstrate a tunable optical buffer with variable time delays for label switching applications using an optical single sideband modulator in a fiber Bragg grating-filter loop. This optical buffer realizes payload storage with optional wavelength conversion function, providing flexibility in packet router design. Small sensitivity penalty is observed in our experiment after the payload circulating in the buffer loop three times. The cascadability of the tunable optical buffer is investigated. We provide analysis of the optical signal to noise ratio degradation due to accumulated amplified spontaneous emission noise, and the penalty caused by loss ripple and group delay ripple of the fiber Bragg grating.     

Experimental demonstration of tunable multiple optical orthogonal codes sequences-based optical label for optical packets switching

In this paper, the tunable multiple optical orthogonal codes sequences (MOOCS)-based optical label for optical packet switching (OPS) (MOOCS-OPS) is experimentally demonstrated for the first time. The tunable MOOCS-based optical label is performed by using fiber Bragg grating (FBG)-based optical en/decoders group and optical switches configured by using Field Programmable Gate Array (FPGA), and the optical label is erased by using Semiconductor Optical Amplifier (SOA). Some waveforms of the MOOCS-based optical label, optical packet including the MOOCS-based optical label and the payloads are obtained, the switching control mechanism and the switching matrix are discussed, the bit error rate (BER) performance of this system is also studied. These experimental results show that the tunable MOOCS-OPS scheme is effective.     

Orthogonal labelling scheme using inverted RZ as payload

In this paper, we present an orthogonal labelling scheme using inverted return-to-zero (IRZ) as payload and differential-phase-shift-keying (DPSK) as label. Transmission performances of orthogonal labelling with 40 Gb/s IRZ payload and 10 Gb/s label are evaluated. Simulation results show that orthogonal labelling using IRZ as payload exhibits a much larger extinction ratio margin than that of using return-to-zero (RZ) as payload. The asynchronous effect between payload and label on the transmission performances of orthogonal labelling using IRZ and RZ as payload is evaluated. Simulation results show that the degradation of asynchronous orthogonal labelling using IRZ as payload is relatively worse than that of using RZ as payload. The impact of optical filter bandwidth before receivers is also investigated. Results show that the receiver sensitivities of label for IRZ/DPSK and payloads for both IRZ/DPSK and RZ/DPSK are degraded with the reduction of the filter bandwidth, while the label of RZ/DPSK exhibits an opposite trend.     

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.     

Applications of optical duobinary in optical carrier suppression and separation labeling

A novel approach is used to implement optical carrier suppression and separation （OCSS） labeling. Then, the performance of 10/40-Gb/s duobinary payload with 2.5-Gb/s amplitude shift keying （ASK） or duobi- nary label by numerical simulations is studied. Influencing factors, such as demultiplexer bandwidth and fiber Bragg grating （FBG） filter bandwidth, are investigated. Simulation result shows that the received sensitivity of ASK label is higher than that of the duobinary label, while the received sensitivity of duobi- nary payload with duobinary label is higher than that with ASK label.     

A novel scheme of two-dimension time-stacked wavelength-time optical code label for optical packet switching network

A novel scheme of time-stacked optical code label based on optical code division multiple (OCDM) technique for optical packet switching network is proposed, in which two-dimensional wavelength-time OCDM code is used as the optical label. Packet loss rate and system characteristic based on the proposed scheme are studied. Results show that less packet loss rate of proposed scheme can be achieved as compared with that of one-dimension time-stacked optical code label system.     

Key Technologies for Optical Packet Switching

The paper describes our recent progress on key technologies and components for realizing optical packet switching,including an out-of-band optical label switching technique, an optical packet synchronizer and a burst-mode optical receiver.     

A novel all-optical label processing based on multiple optical orthogonal codes sequences for optical packet switching networks

This paper proposes an all-optical label processing scheme that uses the multiple optical orthogonal codes sequences (MOOCS)-based optical label for optical packet switching (OPS) (MOOCS-OPS) networks. In this scheme, each MOOCS is a permutation or combination of the multiple optical orthogonal codes (MOOC) selected from the multiple-groups optical orthogonal codes (MGOOC). Following a comparison of different optical label processing (OLP) schemes, the principles of MOOCS-OPS network are given and analyzed. Firstly, theoretical analyses are used to prove that MOOCS is able to greatly enlarge the number of available optical labels when compared to the previous single optical orthogonal code (SOOC) for OPS (SOOC-OPS) network. Then, the key units of the MOOCS-based optical label packets, including optical packet generation, optical label erasing, optical label extraction and optical label rewriting etc., are given and studied. These results are used to verify that the proposed MOOCS-OPS scheme is feasible.     

Separation of label and payload using FP-SOA

A novel scheme of separating the label and payload with different pulse width by using FP-SOA is proposed in this paper. Due to the facet reflectivity of FP-SOA, the gain is rippled with the variation of carrier density and the opposite characteristics of gain and carrier density appear at either side of the gain peak. Since the different pulse widths deplete different number of carriers, the working region in carrier density shifts adaptively with the pulse width. The wide pulse label extraction can be performed in the region where the gain decreases with the increment of carrier density. The label suppression can be realized in another region where the gain increases with increment of carrier density. The numerical simulation shows that the label extraction with 10.5 dB contrast ratio and the label suppression with 7 dB. The application in 10 Gb/s optical packet switching is discussed. The relationship of the pulse peak gain and pulse width is investigated on considering the impact of the pulse peak power and pulse period.     

Improvement of switching properties and cascadability of an ultra-fast reconfigurable optical crosspoint switch matrix using DPSK payloads

In this paper, we demonstrate mitigation of pattern-induced degradation in an optical crosspoint switch (OXS) matrix by utilizing differential phase shift keying (DPSK) modulation format. We experimentally demonstrate 4 × 4 unicast optical packet switching and dynamic reconfiguration for 4-channel, 200 GHz spacing of RZ-DPSK payloads. Reconfigurable time as fast as 2 ns is achieved owing to the optimized control circuit and device fabrication. The power and wavelength dependence are obtained for the RZ-DPSK payload. We also investigate the cascadability of the OXS based on re-circulating loops. Due to the great suppression of the pattern effect in OXS, DPSK has shown dramatical improvement of switching properties compared to conventional ON-OFF keying (OOK) signal. The DPSK payload can outperform OOK for 3.2 dB after 9 hops optical switching.     

Photonic Packet Switching Based on Optical Label Processing

We express a photonic packet switch prototype based on optical label processing methods which dramatically increase the label processing capability. We experimentally demonstrate 40Gbit/s/port packet switching and optical buffering capabilities of the prototype.     

光分组交换网络中多组光正交码组合光标签识别处理及实验

报道了光分组交换网络中基于多组光正交码组合光标签的识别与接收实验,光标签采用了码长为19,码重为3的2组光正交码组合光标签方案.给出了基于多组光正交码光标签的光分组交换网络(MOOC-OPS)基本原理,通过分析指出在MOOC-OPS网络中处理多组在时域上非连续、随机、突发光标签是现实MOOC-OPS关键技术之一.设计出了基于展宽网络和放大器级联方式接收多组低功率窄脉冲(MOOC-OPS网络的光标签)的实验方案,完成了实验电路板制作与实验验证.实验结果表明成功地实现了MOOC-OPS网络中周期为2ns基于多组光正交码光标签脉冲的识别接收,验证了该方案的可行性.     

Investigation of the influence of the key parameters onthe system performance in all-ptical label switching based on FSK/ASK orthogonal modulation format

<正>The transmission characteristics of the optical label switching system based on the FSK/ASK orthogonal modulation format is investigated.The factors that affect the transmission performance,such as the FSK tone space,dispersion compensation and coupler split ratio,are studied by numerical simulation.The proposed scheme is also experimentally demonstrated with a transmission of 155 Mbit/s FSK label combined with 10 Gbit/s ASK payload.     

Transmission performance of the SCM label in optical label switching networks

We have investigated the transmission performance of the label signal in the optical double sideband subcarrier multiplexing (DSB-SCM) label switching link and clarified that the degradation of the label signal results from the fiber chromatic dispersion and the incomplete filtering out of the payload carrier. Our theoretical results show that the DSB-SCM label can immune the fading effect, and the degradation mainly results from the crosstalk from the payload and the time shift of the code edge. The deep suppression of the optical carriers at the receiver can eliminate the crosstalk. The time shift of the code edges leads to the eye closure of the label codes and is independent of the code rate, but it does not degrade the label code with a low bit rate greatly, although it is serious for the label with a high bit rate and ultimately limits the transmission distance of the label. The simulation results validate our analysis very well. As we theoretically predict that the single sideband (SSB)-SCM can eliminate the time shift of the code edges and extend the transmission distance of the label signal.     

155~Mb/s——10~Gb/s combined FSK-IM/optical label-packet modulation signals 100~km transmission over standard single mode fiber using mid-span spectral inversion by four-wave mixing in an SOA

This paper introduces the mid-span spectral inversion by four-wave mixing in a commercially available semiconductor optical amplifier (SOA) with a length of about 1.5~mm to optical label switching network based on combined frequency shift keying (FSK)-intensiy modulation (IM)/optical label-packet modulation to overcome the dispersion limitation of fiber. The 155~Mb/s--10~Gb/s combined FSK/IM signal is experimentally transmitted over a 100~km standard single mode fiber. 10^-10 and 10⁹ BER (bit error ratio), or even better, is achieved for the FSK label and IM packet, respectively. The -19~dB power conversion efficiency is obtained for -1~nm wavelength detuning.     

Research on application of MOOC in optical packet switching

An experiment on receiving and identifying multiple optical orthogonal codes （MOOC） sequence-based optical labels in an optical packet switching （OPS） network is reported. Two groups of MOOC with a code length of 23 and a code weight of 3 are used to identify the optical labels. The scheme and principle of OPS networks based on MOOC sequence-based optical labels are presented. Because optical labels contain OPS and routing information, the importance of optical label processing with multiple inconsecutive, random, and burst optical labels in an OPS network is pointed out. Considering the MOOC-based optical labels, we design a circuit consisting of a broadened network and a cascaded amplifier to receive multiple groups of low-power narrow pulses （optical labels in the MOOC-OPS network） with a period of 2 ns. The successful experimental results demonstrate that the designed scheme is feasible.