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We propose a modified single-carrier frequency domain equalization (SC-FDE) scheme implemented in directly detected wavelength-division-multiplexed passive optical networks (WDM-PONs). A time-clipping technique is used in FDE to perform noise filtering. In the simulation, where the channel is modeled with chromatic dispersion and direct detection, performance improvement is achieved by exploring the clipping position and retained gradient vector length. In the experiment, we investigate the time-clipping SC-FDE implemented in 10-Gb/s direct-detected WDM-PON using an uncooled free-running 1550-nm vertical cavity surface emitting laser. After 30-km transmission, it is observed that the time-clipping scheme can bring roughly 1-dB power penalty improvement over conventional equalization schemes.

An optical switch with load balancing capability can play important roles in reducing power consumption, enhancing scalability, and optimizing bandwidth utilization for data centers. This letter proposes a novel scheme to build up such an optical switch fabric using polarization division multiplexing. In the switch, the functions of load balancing and switching are simultaneously performed by two orthogonal polarizations, respectively. This feature allows the switch to double its throughput without an increase in its port count or reconfiguration speed. A 1 × 32 optical load-balanced switch with this scheme is successfully demonstrated. Experimental results show that the switch exhibits good polarization independence and the average power penalty is 1.3 dB.

In this letter, we propose and experimentally demonstrate an all-optical modulation format conversion scheme from amplitude shift keying (ASK) and quadrature phase shift keying (QPSK) to 8-ary quadrature amplitude modulation (8QAM), using four-wave mixing (FWM) effect in highly nonlinear fiber. In the FWM process, a 20-Gbits/s return-to-zero QPSK (RZ-QPSK) signal and a 10-Gbit/s ASK signal are utilized as probe light and pump light, respectively. A 30-Gbits/s RZ-8QAM signal, which is the idler light, is successfully obtained with optical signal-to-noise ratio larger than 30 dB and bit-error rate lower than 10-5.

The exponential increase in the data center network traffic has posed new challenges for achieving high throughput, low latency and energy consumption. To address these challenges, this paper presents a novel scheme that combines optical circuit and packet switching technologies together in a single optical cross-connect for data center networks. By utilizing fast tunable linecards and parallel array waveguide grating routers, the optical cross-connect can offer low latency, large scalability and high throughput in datacenter networks. A scheduling technique is designed to simultaneously accommodate circuit switching and packet switching in the optical cross-connect. The physical performance of this optical cross-connect in circuit and packet switching modes is investigated by experiments. In addition, the network performance of the optical cross-connect is evaluated through simulations under a mixed circuit/packet-switched traffic pattern. Results show that the network performance of the optical cross-connect does not degrade significantly with an increase in the number of racks, but it is affected by the circuit-switched traffic proportion.

We propose a method to precisely detect the faulty branch of time-division-multiplexing-passive optical networks (TDM-PONs) by encoding the probe signal with optical orthogonal codes. The proposed technique projects each probe signal response onto an orthogonal space, wherein an event corresponding to each branch of the TDM-PON is uniquely mapped onto an orthogonal basis and thereby able to isolate the origin of the event to a particular branch. A proof-of-concept experiment is carried out on a 1 × 16 TDM-PON with 20 km feeder fiber and the results confirm that, with the proposed design the system can support up to 120 m branch fiber length with 3 m spatial resolution.

We propose a novel downlink optical carrier remodulated wavelength-division-multiplexed passive optical network (WDM-PON) architecture, in which two WDM-PONs whose wavelength locate in different wavebands share a single delay interferometer (DI) in remote node (RN) to demodulate the downlink data simultaneously. 10-Gb/s downlink differential phase-shift-keying (DPSK) signal and 1.25-Gb/s remodulated uplink On-Off keying (OOK) signal are generated and measured. Experiment results show that crosstalk between the two WDM-PONs is negligible even though the two PONs share a single DI. With our novel scheme, the single DI can be shared by more users in different PONs, which can reduce the cost of optical network unit (ONU). Meanwhile, Rayleigh backscattering noise is eliminated by combining these two PONs with different wavebands.

In this paper, we demonstrate the full-duplex radio-over-fiber (RoF) system operating in the 60 GHz band and gigabit Ethernet services in the integrated RoF/optical network architecture. The proposed full-duplex 60 GHz RoF system incorporates the centralized photonic upconversion, using the fiber-optic wavelength conversion technique and the envelope detection/direct optical modulation techniques in the 60 GHz band. The RoF system comprises physical link of a 34 km fiber between the central station and the base stations (BSs) with the 5 m aerial distance between the BS and the customer unit for end-user access. The analog performance of the photonic upconversion function are measured and characterized to map the ranges of optical conditions for stable operation, the modulations depth and the spurious-free dynamic range (SFDR). The SFDR above 80.0 dB.Hz2/3 is obtained for the probe wavelength ranged from 1540 to 1555 nm at the bias voltage of -0.8 V. The optimum modulation depth is shifted from -1.0 to -0.5 V correspond to the probe wavelength from 1560 to 1530 nm. The downlink bit-error-rate performance shows direct relationship with its modulation efficiency changes for bias voltages and pump wavelengths.

It is experimentally shown that six-channel C + L-band 80-GHz short pulse trains are generated based on parametric process in highly-nonlinear fiber (HNLF). By launching a pulsed pump and three-channel continuous wave (CW) lights into 1-km HNLF, three-channel signals are amplified and three-channel idlers are generated. The waveforms of the generated 80-GHz short pulses are measured by an auto-correlator. The bit-error-rate (BER) of each channel is analyzed numerically. In the back-to-back case, the power penalties of the generated channels are less than 1.5-dB.

A scheme for hi-fi all-optical continuously tunable delay is proposed. The signal wavelength is converted to a desired idler wavelength and converted back after being delayed by a high linear-chirp-rate (HLCR) fiber Bragg grating (FBG) based on four-wave mixing (FWM) in a highly-nonlinear photonic crystal fiber (HN-PCF). In our experiment, 400 ps (more than 8 full width of half maximum, FWHM) tunable delay is achieved for a 10 GHz clock pulse with relative pulse width broaden ratio (RPWBR) of 2.08%. The power penalty is only 0.3 dB at 10 −9 BER for a 10 Gb/s 2 31 −1 pseudo random bit sequence (PRBS) data.

In this paper, an optically controlled loop buffer is proposed and experimentally demonstrated. It utilizes a semiconductor optical amplifier (SOA) based loop mirror as a fast switch to realize the writing and reading of packets within this buffer and a circulator based optical reflector to achieve internal re-circulations. By adding fibers with different lengths between the loop mirror and the circulator, variable delay time per circulations can be obtained. We also demonstrate the performance of the 2.5 and 10 Gb/s data packets in this buffer structure, as well as the influence of the two different control signal formats on the packet signal degradation during buffering. This loop buffer has the merits of low cost and improved performance compared to other similar loop buffer structures. According to the obtained results, the achieved number of circulations is greatly increased.

We mathematically analyze and experimentally investigate the characteristics of subcarrier-modulated (SCM) light. Our investigation shows that the baseband data are also carried on the optical carrier after subcarrier modulation. This residual data introduce crosstalk when the optical carrier is separated from subcarriers and reused for uplink data modulation. The influence of the residual data carried on the optical carrier is studied in three kinds of upstream transmissions based on wavelength-seeded reflective semiconductor optical amplifiers (RSOAs) for carrier-reuse wavelength-division-multiplexed-passive optical networks (WDM-PONs). Results show that the crosstalk can be significantly suppressed with proper selection of the seeding power and operation conditions of downlink Mach-Zehnder modulator (MZM), including driving voltage and bias voltage.

An integrated configuration is proposed to convert tunable slow light from signal to another frequency in a wide bandwidth by using a 70 m-long highly nonlinear photonic crystal fiber (HN-PCF). A 10 GHz RZ signal is delayed by a 10 Gbit/s 231-1 pseudo random bit sequence (PRBS) stimulated Brillouin scattering (SBS) pump, and the slow light is converted to another frequency in a broadband by four-wave mixing (FWM). By this way, not only the slow light is converted, but the idler power is enhanced greatly. In our experiment, all-optical controlled 37.5 ps delay time is converted in a 40 nm bandwidth flatly, and 4.7 dB idler power is enhanced simultaneously. The experimental results are in good agreement with those of the theory.

The idler is separated from the co-propagating pump in a degenerate four-wave mixing (DFWM) with a symmetrical parametric loop mirror (PALM), which is composed of two identical SOAs and a 70 m highly-nonlinear photonic crystal fiber (HN-PCF). The signal and pump are coupled into the symmetrical PALM from different ports, respectively. After the DFWM based wavelength conversion (WC) in the clockwise and anticlockwise, the idler exits from the signal port, while the pump outputs from its input port. Therefore, the pump is effectively suppressed in the idler channel without a high-speed tunable filter. Contrast to a traditional PALM, the DFWM based conversion efficiency is increased greatly, and the functions of the amplification and the WC are integrated in the smart SOA and HN-PCF PALM. (C) 2008 Elsevier B.V. All rights reserved.

We propose and demonstrate a 10 Gb/s wavelength division multiplexed passive optical network (WDM-PON) where subcarriers are employed to transmit the downstream data and optical carriers of the downlink subcarrier modulated (SCM) lights are reused to injection lock Fabry-Perot laser diodes (FP-LDs) for uplink transmission. Experiment results show that a very good BER performance can be achieved for both uplink and downlink at 10 Gb/s. The impact of optical carrier to subcarrier ratio and wavelength mismatching is also investigated.

In this paper, we analyze the survivability of wavelength division multiplexed (WDM) passive optical network (PON). We propose and experimentally demonstrate a novel survivable WDM-PON architecture with self-protection and in-service fault localization capabilities. Two WDM-PONs are combined together and multiple sub-ring architecture is formed. Protection switching is achieved automatically at optical network units (ONUs) when failure occurs. Fiber loss, fiber fault localization and automatic protection switching in each ONU are real-time monitored in central office (CO) without interrupting customer service. No signaling for failure notice or protection switching is required for either CO or ONUs. Extra fibers required for protection are minimized compared with previous protection schemes. The self-protection and in-service fault localization capabilities of the proposed WDM-PON architecture are experimentally verified.

Various optical-delay buffer architectures and delay media that are suitable for use in optical packet switches are discussed in this paper. In particular, a novel type of folded-path buffer architecture that can provide a large range of variable delays will be described in detail. This buffer is able to dynamically reconfigure itself within nanoseconds due to the use of high-speed ON-OFF optical-signal reflectors. Three different types of such reflectors are proposed, and their performances are measured and compared against one another with the aid of a simulation model. In addition, the optimal operating conditions for the reflectors will be determined so that the optical buffer can provide the maximum range of delay values, while incurring the least power penalty. An example of a performance-optimized optical buffer with multiple sections will also be provided to illustrate how variable delays, ranging from a few nanoseconds to tens of microseconds, can be achieved.

We report our recent research results in the area of optical label switching (OLS) for next-generation optical packet-switched networks. These include optical label generation, label swapping, optical time-delay buffering, clock recovery (CR), and wavelength conversion for optical packets.

We propose a configuration for suppressing pumps in a broad-and flat-band tunable nondegenerate four-wave mixing (FWM) wavelength converter. The signal and pumps are coupled into a highly nonlinear photonic crystal fiber symmetrical Sagnac loop. After the FWM wavelength conversion in the loop, the idler is separated from the pumps without a filter. In our experiment, a flat wavelength conversion bandwidth of 36 nm, conversion efficiency of -11 dB, pump-to-signal suppression ratio of 48 dB, and idler-to-pump suppression ratio of 15 dB are achieved.

We demonstrate the 60-GHz radio-over-fiber downlink adopting the fiber-optic upconversion process. The cross-absorption modulation (XAM) in the multiple-quantum-well electroabsorption modulator (MQW-EAM) is incorporated for the fiber-optic upconversion. Error-free transmission of the 1.25-Gb/s and 622.08-Mb/s pseudorandom bit sequence data is achieved without critical power penalties after the fiber transmission up to 34 km followed by 1-m wireless transmission between the base station and the customer unit. The system performance is dependent on the bias voltage asserted to the MQW-EAM due to the bias-dependent modulation characteristics of XAM and absorption changes. The optimum performance is obtained at the bias of -0.8 V.

We experimentally demonstrate a novel and simple method to generate a dark return-to-zero (RZ) pulse with tunable pulsewidth and extinction ratio by using a dual-arm LiNbO /sub 3/ intensity modulator. Our experimental results show that this dark RZ pulse signal can be used in a 10-Gb/s optical packet switching system as an optical label. In addition, we demonstrate that this dark RZ label can be easily erased using the gain saturation effect in a semiconductor optical amplifier.

We proposed and demonstrated a novel scheme to realize wavelength-selective reconfigurable optical delay buffers using optical fiber delay in a folded-path architecture. The experimental results show that multiple wavelength 10-Gb/s dense wavelength-division-multiplexed packets with 50-GHz channel spacing can individually be delayed a variable amount of time simultaneously with a power penalty less than 1 dB using the proposed reconfigurable buffer architecture

A constant-intensity modulation format such as differential phase-shift-keying is in principle immune to XGM-induced crosstalk in SOAs. We report the reduction of crosstalk in a bidirectional system and successfully realize 16 × 10-Gb/s DWDM signals transmission over 80-km SMF-28 using a DPSK modulation format for the first time. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 525–527, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21036

A novel all-optical buffer based on adjustable time delay line is proposed and experimentally demonstrated. This physically compact buffer can be used in optical packet routers and is dynamically reconfigurable within nanoseconds. By using a flexible folded-path architecture design, packets are controlled to exit the buffer immediately or after a variable delay time. Furthermore, this functionality is achieved without sacrificing the scalability and compactness of the design.

We experimentally investigate the BER performance of a wavelength-tunable directly-modulated laser that can be used in future 100-Gb/s EPON systems. The effects of temperature variation and optical filtering on the receiver sensitivity are also discussed.

We propose a composite optical crossconnect by adding a fast wavelength routing module to a MEMS-based switch. This crossconnect efficiently addresses the requirements of burst and circuit switching in data center optical networks.

Load balancing is an attractive technique to achieve maximum throughput and optimal resource utilization in large-scale switching systems. However current electronic load-balanced switches suffer from severe problems in implementation cost, power consumption and scaling. To overcome these problems, in this paper we propose a single-stage optical load-balanced switch architecture based on an arrayed waveguide grating router (AWGR) in conjunction with fast tunable lasers. By reuse of the fast tunable lasers, the switch achieves both functions of load balancing and switching through the AWGR. With this architecture, proof-of-concept experiments have been conducted to investigate the feasibility of the optical load-balanced switch and to examine its physical performance. Compared to three-stage load-balanced switches, the reported switch needs only half of optical devices such as tunable lasers and AWGRs, which can provide a cost-effective solution for future data centers.

A large scale wavelength division multiplexed passive optical network is proposed and experimentally demonstrated. 124 bidirectional optical channels with 10-Gb/s downstream and 1.25-Gb/s upstream transmission are simultaneously distributed by a single 32*32 cyclic AWG. The effect of the extinction ratio and seeding power to BER performance are experimentally investigated. The selection of the subcarrier frequency is also analyzed by simulation.

We demonstrate, for the first time, an injection-locked Fabry Perot laser operating at 20-Gb/s. This laser can be deployed in wavelength-division-multiplexing OFDM-PONs. Intensity modulation and direct detection are used and 0.5-dB SNR penalty is observed after 52-km fiber.

Compared with backup sharing in WDM networks, it is more complex and challenging to share backup resources in OFDM-based optical networks with elastic bandwidth allocation. We propose and evaluate conservative and agressive backup sharing policies.

In this paper, we introduce our Home2015 project - wavelength-agile optical access networking system. We propose a multi-wavelength access network to offer higher system capacities for next-generation optical access. Our proposed concept of virtual PON (VPON) is introduced to realize dynamic ONU re-grouping functionality. Optical network units (ONUs) in the PON system can dynamically form different TDM-PON by using a different downlink and uplink wavelength channel. Novel photonic silicon chip integration techniques are introduced to reduce size and cost of the ONUs. We also introduce our works on live 3D hologram video transmission platform design and live 3D hologram video transmission via the 10-Gb/s wavelength-agile optical access network. Our demostration shows that our system has good transmission performances.

Combining subcarrier multiplexing and wavelength division multiplexing techniques, we demonstrate a 124-channel hybrid PON with 10-Gb/s downstream and 1.25-Gb/s upstream transmission. A single 32∗32 AWG is used to distribute the bidirectional wavelength channels for 124 users.

By combining XGM, and cascaded FWM effects in an SOA, seven multicast channels with 100-GHz spacing are demonstrated using single pump laser source. The power penalty of these multicast channels is less than 3.3 dB.

We demonstrate a 60-channel wavelength division multiplexed passive optical network (WDM-PON) with 10-Gb/s bidirectional transmission. A single 32*32 AWGR is used at the remote node to achieve a total system capacity of 1.2 Tbit/s.

We review recent work on all-optical wavelength multicasting based on various techniques. We introduce two four-wave mixing based multicasting schemes; one is in highly nonlinear fiber loop mirror, the other is of reduced polarization sensitivity. (2 pages)

With the increase of SRLGs, availability of shared-path protection deteriorates significantly. We propose availability-aware SRLG failure protection and heuristics by satisfying availability requirements while minimizing spare capacity usage.

In this paper, we propose and demonstrate the practical all-optical wavelength multicasting scheme based on the four-wave mixing (FWM) effect in both a highly nonlinear fiber (HNLF) and a semiconductor optical amplifier (SOA). Then we carry out comprehensive comparisons of the performance differences between using the HNLF and SOA for this proposed multicasting scheme. Seven multicast channels are experimentally demonstrated by using three co-polarized probes and a modulated signal. The merit of the proposed scheme is that the polarization sensitivity is significantly reduced from more than 20 dB to approximately 5 dB using the HNFL and 2.5 dB using the SOA. The low polarization sensitivity leads to a difference of less than 1 dB in the power penalty of the multicast channels at bit error rate . In addition, we compare the multicasting performance of the OOK and differential phase-shift keying (DPSK) signals using the proposed scheme and found that the power penalties of the DPSK multicast channels in the HNLF and the SOA are less than 1.25 and 1.1 dB respectively, and the power penalties of the OOK multicast channels are less than 1.5 dB and 3.1 dB in the HNLF and the SOA, respectively.

The convergence of WDM layer and Ethernet layer in metro networks will offer tremendous benefits to simplify network management and optimize network resources. A control plane approach will more efficiently facilitate a carrier-grade Ethernet MAN/WAN. We discuss our research and experiment work on applying GMPLS control plane over an integrated optical Ethernet network to provide carrier-grade Ethernet services, including QoS and survivability in an efficient way.

For the first time, the quasiperiodic Bragg fibers with geometrically distributed multilayered cladding are proposed and analyzed. We demonstrate that hollow-core Bragg fibers with quasiperiodic dielectric multilayer cladding can achieve low loss transmission over a broadband wavelength range of more than an octave (from 0.81 μm to 1.7 μm). The periods of the Bragg blocks follows a geometrical progression with a common ratio r

International audience; We present a new, endless polarization control method based on two rotatable wave plates with variable birefringence. We propose two boundary conditions for the parameters of the wave plates so that this method will not have the pole problem. The pole problem is one of the main weaknesses in reset-free polarization controllers. We experimentally demonstrate the control principle of this method and verify its feasibility by using a simple feedback mechanism.