Measurement on Spot Size Dependence of Dense WDM Dielectric Multilayer Filters

We present the spot size dependence of dielectric multilayer filters for use in dense WDM systems. We found large dependences of filter performances on the spot size and the incident angle of input light, which should be important for miniaturizing multi-channel add/drop filters.     

Complete Distributed Hyper-Entangled-Bell-State Analysis and Quantum Super Dense Coding

We propose a protocol to implement the distributed hyper-entangled-Bell-state analysis (HBSA) for photonic qubits with weak cross-Kerr nonlinearities, QND photon-number-resolving detection, and some linear optical elements. The distinct feature of our scheme is that the BSA for two different degrees of freedom can be implemented deterministically and nondestructively. Based on the present HBSA, we achieve quantum super dense coding with double information capacity, which makes our scheme more significant for long-distance quantum communication.     

Polarization mode dispersion in WDM systems

The coupled nonlinear Schrodinger equations for two wavelength optical pulses in a birefringence fiber are given. The model for treating polarization mode dispersion in two channel (WDM) system is established. Based on this model, optical signal propagation behaviors in two channel WDM with polarization mode dispersion are numerically simulated. The influences of polarization mode dispersion on two channel WDM system are also analyzed.     

Impact of ASE noise in WDM systems

The small signal analysis method is presented for the discussion of amplified spontaneous emission (ASE) noise in dispersion and nonlinear transmission fibers in wavelength division multiplex (WDM) systems. Based on it, the complete ASE noise spectra (include the ASE noise, the ASE noise enhanced by parametric gain and the crosstalk caused by ASE noise and parametric gain) are described and the factors impacting on them are discussed. The crosstalk caused by ASE noise and parametric gain in single mode fibers, non-zero dispersion shift fibers and dispersion compensation fibers are analyzed. Taking into account the dispersion effect in the transmission fibers, the three types of ASE noise may decrease.     

Analytical investigations on crosstalk in fiber Raman amplification for WDM systems

In this paper, the analytical investigations for the crosstalk in fiber amplification for WDM channels have been reported. The crosstalk between WDM channels with external Raman amplification including second-order dispersion terms has been investigated. It has been shown that the higher-order dispersion severely degrades the performance of optical communication systems. To ensure small crosstalk, the signal gain and the injected pump power should be limited to the value well below the threshold of Raman amplification. Analytical formula for signal interference ratio (SIR) and gain in fiber Raman amplifier including the impact of second-order dispersion terms for WDM systems has been derived at different wavelengths. It has also been shown that there is increase in crosstalk due to second-order dispersion.     

Dense coding capacity in correlated noisy channels with weak measurement

Capacity of dense coding via correlated noisy channel is greater than that via uncorrelated noisy channel. It is shown that the weak measurement and reversal measurement need to further improve their quantum dense coding capacity in correlated amplitude damping channel, but this improvement is very small in correlated phase damping channel and correlated depolarizing channel.     

Bit-pattern-dependent polarization rotation in first-order PMD-compensated WDM systems

We demonstrate both numerically and experimentally that the phase-change due to fiber nonlinearities induces a bit-pattern-dependent rotation of the state-of-polarization which translates to uncertainty in the principal states of polarization. This effect severely limits the performance of the first-order PMD post-compensation and suggests the use of in-line compensators. Our simulation shows that fiber nonlinearities cause significant distortion (more than 4-dBm Q-penalty after 600-km transmission at 10 Gbit/s) after first-order PMD compensation. For optical powers as low as 3 dBm/channel in systems where PMD is not uniformly distributed along the transmission link, first-order PMD compensation may be ineffective.     

Dispersion-Compensating Graded Index Multiclad Fiber: Optimization for Dispersion-Managed WDM Transmission Systems

This work reports the design optimization of a single-mode graded index multiclad dispersion-compensating fiber (DCF) with a central dip, for broadband wavelength division multiplexing (WDM) system in the C- and L-bands of an operating wavelength zone. The index profile parameters of this fiber have been adjusted to simultaneously achieve high figure of merit (FOM) as well as considerably high value of effective core areas of the fiber to minimize the nonlinear effects like self-phase modulation or cross-phase modulation. At 1,550 nm operating wavelength, an effective core area (A_eff) of 46 μm², which is very large compared to other reported values of DCFs, is obtained here. The average dispersion of the DCFs, in combination with conventional single-mode fiber (CSF) and small dispersion fiber (SDF), are found out to be considerably flat in the entire C- and L-band zone of operating wavelength.     

Effect of four-wave mixing in WDM optical fibre systems

Wavelength division multiplexing (WDM) can both significantly enhance transmission capacity and provide more flexibility in optical network design. Through the use of erbium-doped fibre amplifiers (EDFAs), it is possible to build long-distance transparent optical transmission links without electrical regenerators. In such systems, fibre nonlinearities are likely to impose a transmission limit due to increased total interaction length. There are a number of optical nonlinear effects in optical fibres, such as stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), carrier-induced phase modulation and four-wave mixing (FWM). Out of these SRS and FWM are the dominant effects. In this paper, an algorithm has been suggested to study the effect of FWM in the total system noise considering the combined effect of SRS and FWM in the presence of amplified spontaneous noise (ASE). It has been found from the study that to maximize the signal-to-noise ratio of the transmitted signal in a WDM system FWM noise needs to be reduced as this is the dominant noise factor.     

Design and optimization of high-performance microring-based uni-traveling carrier photodiode for WDM optical systems

This paper presents the design principles of a novel optimized microring-based uni-traveling carrier photodiode (MR-UTC-PD), for wavelength division multiplexing (WDM) optical systems. The fundamental parameters for output characteristics such as quantum efficiency and 3-dB bandwidth of MR-UTC-PD are discussed. We analyze the effects of basic parameters as effective ring radius, definite coupling condition and the suitable cross section on the MR-UTC-PD main characteristics for high performance of the device. It is shown that the maximum quantum efficiency and most efficient performance of the device can be obtained at critical coupling condition. We show that the maximum 3-dB bandwidth and an efficient approach for high bandwidth-efficiency product can be achieved at overcoupling condition. In this regard, some design curves are presented for the optimized MR-UTC-PD.     

Performance Optimization of Dispersion-Managed WDM Systems Based on Four-Wave Mixing

We systemically investigate the interchannel four-wave mixing (FWM) in dispersion-managed WDM systems with arbitrary launch position. We optimize the number of fiber sections, and the dispersion ratio for the system performance.     

Crosstalk reduction in WDM systems using hybrid amplification technique

To reduce the crosstalk, polarization interleaved WDM systems is modified and analyzed. In line compensation is carried out via the hybrid amplification technique. The performance of the system is evaluated with signal power, OSNR, noise power, and optical eye-diagram. The modified system yields better results.     

Super high-power laser systems and their application

Super high-power laser systems have been studied. GEKKO XII glass laser, LEKKO VIII CO₂ laser, diode-pumped solid-state laser and PW cpa Nd glass laser have been developed at Osaka University. They have proved to be very effective for laser fusion research. Various applications in the wide fields are presented.     

A Class of Super Dense Stars Models Using Charged Analogues of Hajj-Boutros Type Relativistic Fluid Solutions

We present a spherically symmetric solution of the general relativistic field equations in isotropic coordinates for perfect charged fluid, compatible with a super dense star modeling. The solution is well behaved for all the values of Schwarzschild parameter u lying in the range 0 < u < 0.1727 for the maximum value of charge parameter K = 0.08163. The maximum mass of the fluid distribution is calculated by using stellar surface density as ρ _b = 4.6888×10¹⁴g cm^?3. Corresponding to K = 0.08 and u _max = 0.1732, the resulting well behaved solution has a maximum mass M = 0.9324M _⊙ and radius R = 8.00 and by assuming ρ _b = 2×10¹⁴g cm^?3 the solution results a stellar configuration with maximum mass M = 1.43M _⊙ and radius R _b = 12.25 km. The maximum mass is found increasing with increasing K up to 0.08. The well behaved class of relativistic stellar models obtained in this work might has astrophysical significance in the study of internal structure of compact star such as neutron star or self-bound strange quark star like Her X-1.     

Proof-of-concept implementation of the massively parallel algorithm for simulation of dispersion-managed WDM optical fiber systems

We perform a proof-of-concept implementation of the massively parallel algorithm [P. M. Lushnikov, Opt. Lett. 27, 939 (2002)] for simulation of dispersion-managed wavelength-division-multiplexed optical fiber systems. Linear scalability of the algorithm with the number of computer cores is demonstrated. Exact result on the accuracy of the implemented algorithm is found analytically and confirmed numerically as well as it is compared with the accuracy of the standard split-step algorithm.     

Use of fibre gratings for bit skew compensation in all optical bit parallel WDM systems

We demonstrate transmission of two wavelength division multiplexed (WDM) bit parallel channels over 100 km of standard single mode fibre link using direct-modulated laser diodes at 10 Gbit/s channel. Step-chirped fibre gratings are used to simultaneously compensate to bit skew and dispersion. Bit skew of approximately 2.5 ns due to the fibre dispersion is completely compensated. Our work show shows that the step-chirped fibre grating technique can eliminate the bit skew for bit parallel WDM systems operating at Gbit rate over hundreds of kilometres of fibre link.     

Characterization of wavelength interleaving in radio-over-fiber systems employing WDM/SCM

A radio-over-fiber (RoF) distribution system incorporating both sub-carrier multiplexing and wavelength division multiplexing (WDM) technologies is presented. This signal is directly modulated onto three high-speed lasers. Bragg filters are employed at the receiver base station in order to both demultiplex the required optical channel, and ensure that the detected signal is single side band (in order to overcome dispersion limitations of the link). System spectral efficiency is optimised by wavelength interleaving. The channel spacing between the WDM channels is varied and the system performance for different values of channel spacing and spectral efficiencies is investigated. The results show that wavelength interleaving is a reliable technique that could be used to increase the spectral efficiency of RoF systems.     

A maximum algebraic connectivity increment edge-based strategy for capacity enhancement in scale-free networks

In this paper, we focus on how to improve transportation efficiency of scale-free networks via edge increments. Based on analyzing the correlation between algebraic connectivity, which is the second smallest eigenvalue of the graph Laplacian matrix, and traffic capacity, we propose an effective edge-addition strategy called maximum algebraic connectivity increment edge (MACIE). Existing approaches are based on topological structure parameters, such as path and degree of a network, which require expensive computation. Different from existing edge-addition strategies, MACIE enhances transport efficiency by maximizing algebraic connectivity, and thus has a shorter running time. Simulation results show that MACIE is efficient and performs better than the previous strategy of reduction structural hole (RSH).     

Optimization of Generation and Detection of WDM Signals with Advanced Modulation Formats

This paper presents optimal generation and detection of wavelength division multiplexed (WDM) signals with advanced modulation formats. We investigate the relative phase alignment between phase modulation and data bits for chirped return-to-zero (CRZ) signals, and the frequency offset between the RZ carrier and various optical filters for vestigial side band (VSB)-RZ signals.     

Four-wave mixing analysis in WDM optical communication systems with higher-order dispersion

Four-wave mixing (FWM) is one of the major limiting factors in WDM optical fiber communication systems. In this paper, we analyze the individual and combined effect of second-, third-, fourth- and fifth-order dispersion parameters on FWM at different input channel powers and core effective areas, which have not been calculated earlier. FWM power versus channel power graphs for individual and combined effects of dispersion parameters have been presented, and it has been observed that FWM reduces for combined effect of dispersion parameter.