Research on Raman Crosstalk in Broadband Wavelength Division Multiplexed Systems

After a theoretical model is put forward on the base of accurate description of the Raman gain profile and the physical quantity, maximum Raman crosstalk(MRC), which quantificationally depicts the intensity of Raman crosstalk is defined. The influences of launch power, fiber effective core area, fiber nonlinear index, fiber length, channel number and channel interval on MRC are deduced. The result indicates that compared with low speed and narrowband optical fiber communication system, serious Raman crosstalk lies in high speed and broadband system, which impacts the performance of the system badly. The result is useful for forecasting Raman crosstalk in broadband and high speed optical fiber communication system.

Performance of phase-matching quantum key distribution based on wavelength division multiplexing technology

Quantum key distribution(QKD) generates information-theoretical secure keys between two parties based on the physical laws of quantum mechanics. The phase-matching(PM) QKD protocol allows the key rate to break the quantum channel secret key capacity limit without quantum repeaters, and the security of the protocol is demonstrated by using equivalent entanglement. In this paper, the wavelength division multiplexing(WDM) technique is applied to the PM-QKD protocol considering the effect of crosstalk noise on the secret key rate. The performance of PM-QKD protocol based on WDM with the influence of adjacent classical channels and Raman scattering is analyzed by numerical simulations to maximize the total secret key rate of the QKD, providing a reference for future implementations of QKD based on WDM techniques.

A 32-channel 100 GHz wavelength division multiplexer by interleaving two silicon arrayed waveguide gratings

A 32-channel wavelength division multiplexer with 100 GHz spacing is designed and fabricated by interleaving two silicon arrayed waveguide gratings(AWGs).It has a parallel structure consisting of two silicon 16-channel AWGs with200 GHz spacing and a Mach-Zehnder interferometer(MZI)with 200 GHz free spectral range.The 16 channels of one silicon AWG are interleaved with those of the other AWG in spectrum,but with an identical spacing of 200 GHz.For the composed wavelength division multiplexer,the experiment results reveal 32 wavelength channels in C-band,a wavelength spacing of 100 GHz,and a channel crosstalk lower than-15 dB.

Exploiting the Faster-Than-Nyquist Concept in Wavelength-Division Multiplexing Systems Using Duobinary Shaping

This paper begins with Nyquist wavelengthdivision multiplexing （WDM） and then introduces fasterthanNyquist. In fasterthanNyquist a certain amount of intersymbol interference （ISI） is accepted, which violates the fundamental principle of Nyquist WDM. This results in muchrelaxed transceiver bandwidth and simpler spectral design. However, in fasterthanNyquist, implementation complexity is shifted from the transmitter side to the receiver side. Therefore, successful application of fasterthanNyquist depends on innovation in the receiver structure. In this paper, we discuss the guidelines for implementing suboptimum, lowcomplexity receivers based on fasterthanNyquist. We suggest that duobinary shaping is a good technique for trading off achievable spectral efficiency, detection performance, and implementation complexity and might be preferable to Nyquist WDM. Experiments are conducted to verify robustness of the proposed technique.

A new synchronization scheme based on time division multiplexing and wavelength division multiplexing technology for practical quantum key distribution system

Three clock synchronization schemes for a quantum key distribution system are compared experimentally through the outdoor fibre and the interaction physical model of the the clock signal and the the quantum signal in the quantum key distribution system is analysed to propose a new synchronization scheme based on time division multiplexing and wavelength division multiplexing technology to reduce quantum bits error rates under some transmission rate conditions, The proposed synchronization scheme can not only completely eliminate noise photons from the bright background light of the the clock signal, but also suppress the fibre nonlinear crosstalk.

Reference-frame-independent quantum key distribution of wavelength division multiplexing with multiple quantum channels

Reference-frame-independent quantum key distribution(RFI-QKD)can allow a quantum key distribution system to obtain the ideal key rate and transmission distance without reference system calibration,which has attracted much attention.Here,we propose an RFI-QKD protocol based on wavelength division multiplexing(WDM)considering finite-key analysis and crosstalk.The finite-key bound for RFI-QKD with decoy states is derived under the crosstalk of WDM.The resulting secret key rate of RFI-QKD,which is more rigorous,is obtained.Simulation results reveal that the secret key rate of RFI-QKD based on WDM is affected by the multiplexing channel number,as well as crosstalk between adjacent channels.

Silicon-Based Mode Converter and Demultiplexer for Wavelength Division Multiplexing Transmission by Using Multimode Interference Couplers

We present a mode converter and demultiplexer structure for wavelength division multiplexing (WDM) transmission by employing multimode interference (MMI) on Silicon-on-Insulator (SOI) platform. The mode converter and demultiplexer have a compact size of less than 2.7 μm × 43.7 μm. Moreover, the crosstalk between neighboring wavelength channel within C band (1530 nm to 1570 nm) can be reduced by utilizing the tapered phase shifter cascaded with MMI. The simulated results indicate that this structure has a low insertion loss of less than 1 dB, a low crosstalk of better than ?15 dB and a relatively high fabrication tolerance of ~10 nm. Such structure may find many potential applications in silicon photonic integrated devices.

Minimizing FWM Impact in DWDM ROF DP-DQPSK System for Optical

The demonstration of a higher data rate transmission system was amajor aspect to be considered by researchers in recent years. The most relevantaspect to be studied and analyzed is the need for a reliable system to handlenonlinear impairments and reduce them. Therefore, this paper examines theinfluence of Four-Wave Mixing (FWM) impairment on the proposed highdata rate Dual polarization–Differential Quadrature phase shift keying (DPDQPSK)system using the Optisystem software. In the beginning, the impactof varied input power on the proposed system’s performance was evaluated interms of QF and BER metrics. More power is used to improve system performance.However, increasing power would raise theFWMeffects. Accordingly,a−10dBminput power and the proposed system are used to reduce the impactof FWM. Additionally, a hybrid amplification method is proposed to enhancesystem performance by utilizing the major amplification methods of erbiumdopedfiber amplifier (EDFA): semiconductor optical amplifier (SOA) andRadio optical amplifier (ROA). The evaluation demonstrates that the OAEDFAoutperformed the other two key amplification techniques of (EDFASOA)and (EDFA-ROA) in improving Quality factor (QF) and Bit error rate(BER) system results for all distances up to 720 km. Consequently, the methodcontributes to minimizing the impact of FWM. In the future, other forms ofnonlinearity will be investigated and studied to quantify their impact on theproposed system.

A cost-effective structure of a centralized-light-source WDM-PON utilizing inverse-duobinary-RZ downstream and DPSK upstream

In this paper, we propose a new structure of a centralized-light-source wavelength division multiplexed passive op- tical network （WDM-PON） utilizing inverse-duobinary-return-to-zero （inverse-duobinary-RZ） downstream and DPSK up- stream. It reuses downstream light for the upstream modulation, which retrenches lasers assembled at each optical network unit （ONU）, and ultimately cuts down the cost of ONUs a great deal. Meanwhile, a 50-km-reach WDM-PON experiment with 10-Gb/s inverse-duobinary-RZ downstream and 6-Gb/s DPSK upstream is demonstrated here. It is revealed to be a novel cost-effective alternative for the next generation access network.

Optical multiplexing techniques and their marriage for on-chip and optical fiber communication:a review

Herein,an attention-grabbing and up-to-date review related to major multiplexing techniques is presented which in-cludes wavelength division multiplexing(WDM),polarization division multiplexing(PDM),space division multiplexing(SDM),mode division multiplexing(MDM)and orbital angular momentum multiplexing(OAMM).Multiplexing is a mech-anism by which multiple signals are combined into a shared channel used to showcase the maximum capacity of the op-tical links.However,it is critical to develop hybrid multiplexing methods to allow enhanced channel numbers.In this re-view,we have also included hybrid multiplexing techniques such as WDM-PDM,WDM-MDM and PDM-MDM.It is prob-able to attain N×M channels by utilizing N wavelengths and M guided-modes by simply utilizing hybrid WDM-MDM(de)multiplexers.To the best of our knowledge,this review paper is one of its kind which has highlighted the most prom-inent and recent signs of progress in multiplexing techniques in one place.

Technical study of visible light wavelength division multiplexing using polymer optical fiber

Visible light wavelength division multiplexing （VWDM） experiment was performed using polymer optical fiber （POF）. Lights of two different wavelengths （650 and 530 nm） were sent to a single POF. Red light （650 nm） was used for 100-Mb/s full duplex IP data transmission and green light （530 nm） was used for voice signal transmission. Light sources are light-emitting diodes （LEDs）. A POF coupler （splitter） and the prisms were employed as multiplexer and demultiplexer, respectively. The channel isolation and insert loss were measured, which are 20.5 and 17.65 dB for 650-nm channel respectively, and 19.16 and 20.55 dB for 530 nm one respectively.

Analysis of Doppler-effect on satellite constellations with wavelength division multiplexing architectures

With the development of optical space communications, a global space-based optical backbone network is currently proposed by using broadband laser inter-satellite links （ISLs） which enable routing traffic through the space. Satellite optical networking techniques based on wavelength division multiplexing （WDM） ISLs can transit significantly high data rates signals. In this letter, a new function of wavelength excursion due to Doppler-effect is developed for the ISLs, considering the conception of pointing ahead mechanism. The characteristic of wavelength excursion induced by Doppler-effect is examined in one of low earth orbit （LEO） satellite constellation networks named the next-generation LEO system （NeLS） with WDM ISLs assumed, and the influence on its communications caused by wavelength excursion is analyzed.

Power distribution analysis for multiple modulation formats in an all-optical sampling wavelength division multiplexing system

An optimal power distribution analysis for an all-optical sampling orthagonal frequency division multiplexing(OFDM) scheme with multiple modulation formats including diferential phase shift keyed(DPSK), diferential quadrature phase shift keyed(DQPSK), and non-return-to-zero(NRZ) is proposed. The noise tolerances of different modulation formats are analyzed, and the optimal input power ratio between phase and intensity modulation formats for the best overall receiving performance is investigated under unchanged total input power. Moreover, this scheme can seamlessly coexist with the traditional WDM channel.

Design and analysis of multi-channel drop filter using dual L defected hexagonal photonic crystal ring resonator

In this paper,dual L defected hexagonal Photonic Crystal Ring Resonator(PCRR)using Channel Drop Filter(CDF)is designed for Coarse Wavelength Division Multiplexing(CWDM)systems.In this structure,the external rods of the ring resonator are arranged in a hexagon and the internal rods are removed in L arrangement for introducing defects.Scatter rods are used to prevent leakage.By using the L defected hexagonal resonator,a multi-channel CDF is designed,which exhibits multiple wavelengths of CWDM(1500 nm–1600 nm)region.In addition,the selection of rod size and the position of rods in the proposed multi-channel CDF are validated by varying the radius of coupling and scattering rods,as well as the position of resonators,respectively.By using plane wave expansion and opti Finite Difference Time Domain(FDTD)method,the electromagnetic wave propagation and the photonic band gap are obtained.

Analysis of Radio over Fiber system for mitigating four-wave mixing effect

In this paper,an efficient 8-channel 32Gbps RoF(Radio over Fiber)system incorporating Bessel Filter(8/32 RoFBF)has been demonstrated to reduce the impact of non-linear transmission effects,specifically Four-Wave Mixing(FWM).The simulation results indicate that the proposed 8/32 RoF-BF system provides an optimum result w.r.t.channel spacing(75 GHz),input source power(0 dBm)and number of input channels(8).In comparison with the existing RoF system,the proposed 8/32 RoF-BF system has been validated analytically and it is found that the performance of the proposed system is in close proximity particularly in FWM sideband power reduction of the order of 4 dBm for the 8-channel 32Gbps RoF system.

Fiber Bragg Grating Sensor Array System Based on Digital Phase Generated Carrier Demodulation and Reference Compensation Method

A novel fiber Bragg grating （FBG） sensor array system based on digital phase generated carrier （PGC） demodulation and reference compensation method is proposed and set up. Experimental results confirm that the digital PGC demodulation can be used for wavelength-division-multiplexed FBG sensor array and the reference compensation method can reduce the environmental interference by approximately 40 dB in the frequency range from 20 Hz to 2 kHz. The minimum detectable wavelength-shift of the sensor system is 1 × 10^-3 pm/Hz^1/2.

Cyclic polling-based dynamic wavelength and bandwidth allocation in wavelength division multiplexing passive optical networks

Cyclic polling-based dynamic wavelength and bandwidth allocation algorithm supporting differentiated classes of services in wavelength division multiplexing （WDM） passive optical networks （PONs） is proposed. In this algorithm, the optical line terminal （OLT） polls for optical network unit （ONU） requests to transmit data in a cyclic manner. Services are categorized into three classes： expedited forward （EF） priority, assured forwarding （AF） priority, and best effort （BE） priority. The OLT assigns bandwidth for different priorities with different strategies. Simulation results show that the proposed algorithm saves a lot of downstream bandwidth under low load and does not show the light-load penalty compared with the simultaneous and interleaved polling schemes.

Channel Pre-emphasis Equalization for a 270km 40×40 Gbit/s WDM System with Cascaded EDFAs/Raman Amplifiers

Optical channel pre-emphasis equalization is experimentally researched for a 270 km 40 × 40 Gbit/s wavelength division multiplexing （WDM） transmission system with three Erbium-doped fiber amplifiers （ED- FAs） and Raman amplifiers concatenated as booster amplifier. The channel imbalance of the overall system changes with different sets of power launched into EDFAs. By appropriately choosing the power input to concatenated EDFAs, the output spectrum of 40 channel signal can be equalized to the most extent. The merit of benefit can be around 5.5 dB by this pre-emphasis equalization. The requirement for the gain equalizer is therefore greatly released. Then the gain imbalance of the overall system and the power imbalance of 40 channels are compared and the two almost matches, but the significant difference lies on some channels. Finally, the pump power into Raman amplifier is also optimized, and another 1.3 dB improvement of channel equaliza- tion can be further achieved.

A Routing Algorithm in WDM Mesh Networks with Grooming Capacities

Most of the work in traffic grooming has been in the area of providing efficient network designs in Wavelength division multiplexing （WDM）. The objective of these traffic grooming algorithms is to reduce the cost of overall networks. In this paper, a routing algorithm based on transiently chaotic neural network is proposed to solve the problem in WDM logical topology. The objectives of the routing algorithm are ac commodating all traffic requirements and using less network resource. The simulation shows that the proposed algorithm is efficient in the routing selection, meanwhile the algorithm can use less network resource.

Phase modulation polarization encoding module applied to one-to-many QKD network based on wavelength division multiplexing

The quantum key distribution(QKD)network is a promising solution for secure communications.In this paper,we proposed a polarization-independent phase-modulated polarization encoding module,and it can be combined with a dense wavelength division multiplexer(DWDM)to achieve multi-user QKD.We experimentally test the encoding module with a repetition rate of 62.5 MHz,and its average quantum bit error rate(QBER)is as low as 0.4%.Finally,we implement a principle verification test for simultaneous QKD for 1 to 2 users in 100 min,and the average QBER of two users under the transmission distance of 1 km and 5 km is kept below 0.8%.Due to the use of polarization encoding,the module can also realize scalable network architecture in free-space QKD systems in the future.