Volume 40, Issue 2 -

Analysis of wavelength division multiplexing (WDM) system utilizing erbium-doped fiber amplifier (EDFA) has been carried out by many researchers. In this paper, the performance analysis of 8-channel WDM system utilizing EDFA and fiber Bragg grating (FBG) combination is carried out in a wavelength band 1546–1552 nm at 10 Gbps. The performance of three apodization functions (Uniform, Gaussian and Tanh) of FBG is compared using return-to-zero (RZ) and non-return-to-zero modulation formats at fiber lengths 50, 60, 70 and 80 km. Also, the performance of FBG is compared for both aspects: with chirp and without chirp for grating lengths 5–10 mm. The Gaussian apodized and linearly chirped FBG outperformed the other two in compensating chromatic dispersion. Optimum values of Q-factor are also obtained using linearly chirped FBG with RZ modulation format at 10 mm of grating length.

Peak to average power ratio (PAPR) is one of the major limitations of orthogonal frequency division multiplexing (OFDM) systems because the higher PAPR induces the signal to get out of linear region of high power amplifier (HPA). In this article, a hybrid PAPR reduction scheme based on the combination of optimized iterative clipping and filtering (OICF) method and phase rotation is proposed. Using phase rotation, signal’s initial PAPR has been reduced by 14.23 dB and then OICF further reduces the final PAPR by 1.37 dB. Decreased PAPR will play an important role in reducing systems power consumption.

In this paper, an OFDM-ROF-PON transmission system at bit rate of 4×10 Gbps is proposed and demonstrated. This paper analyzes orthogonal frequency division multiplexing system for radio over fiber in passive optical network at different input powers. A laser source of 193.1 THz is used with single mode fibers of length 400 km and 500 km. A transmission bit rate of 10 Gbits/sec is used to simulate the OFDM-ROF-PON system. The performance of the system has been analyzed with acceptable Quality Factor and Bit Error Rate at low signal input power in the presence of fiber non-linearities. Also the system does not use any amplifiers and the work is done at higher bit rates. It is analyzed that as the input power increases quality factor also increases and bit error rate decreases.

Set-Reset (SR) latch or flip-flop is bistabile circuit. The circuit maintains a binary state indefinitely until directed by an input signal (clock signal) to switch state. Sequential logic circuits for specific application can be implemented by using SR flip-flop and external gates. In this article, SR latch and SR flip-flop is proposed using electro-optic effect inside lithium–niobate-based Mach–Zehnder interferometers (MZIs). The MZI structures have the powerful capability of switching an optical input signal to a desired output port. The article constitutes a mathematical description of the proposed device and thereafter simulation using MATLAB. The study is verified using beam propagation method (BPM).

In this article, we proposed a four-channel optical demultiplexer based on photonic crystal resonant cavities. For performing wavelength selection task, we used four resonant cavities with different lengths in order to choose four channels with different wavelengths. The average channel spacing of the structure is about 1 nm and the minimum transmission efficiency is 90 %. The bandwidths of the channels are the same and equal to 0.8 nm.

This paper presents a PON link failure monitoring scheme based on optical pre-coding polling which establishes link failure optimal judgment performance model by using of Neyman-Pearson Criterion. The simulation results show that with the increase of the distance from the user, the NTC becomes wider in the range of optimal judgment, which is easier to achieve optimal judgment; the number of network users is reduced from 128 to 16, NTC in the range of optimal judgment becomes wider; When the pulse width is between 10−11s<Tc<10−9s${10^{ - 11}}s \lt Tc \lt {10^{ - 9}}s$, it is relatively easy to get the optimal decision; When the transmission power Ps≥10−2w$Ps \ge {10^{ - 2}}{\rm{w}}$, the value of ODP is not changed. Therefore, it is possible to reduce the cost of the monitoring system by selecting the appropriate device; and simultaneously selects the optimal system parameters to improve the optimal performance of the monitoring system.

Inter-satellite communication is a free-space optical technology which is used to establish communication between satellites in space. This work is focused on the transmission of 10 Gbps data over 4,000 km inter-satellite communication link by incorporating orthogonal frequency division multiplexing scheme. Moreover, a comparison of 4 quadrature amplitude modulation and 4 phase shift key encoding scheme is also presented in this work. The performance of proposed system is evaluated in terms of signal-to-noise ratio, total received power, radio-frequency spectrum and constellation diagrams.

Optical waveguides were generated in Polymethylmethacrylate using “direct” laser and contact mask structuring. Excimer laser radiation (248 nm) produced a local refractive index increase thereby achieving light guiding in waveguides with widths from 2 to 15 μ$\mu$m. The near field output images were analyzed using visible and infrared laser light. The mode fields of single mode structures were evaluated to elaborate numerically the parameters of the index profile. An index increase up to 0.01 could be achieved using laser pulses at fluences below 0.15$0.15$J/cm2${\textrm{J/cm}^{2}}$. Thus it was possible to design interference couplers of 5 μ$\mu$m waveguides width for the visible (635 nm to 670 nm) as well as for the infrared range at 1550 nm. The coupling properties as a function of the waveguide separation and the wavelength is investigated and found compatible with numerical simulations for the structure design. The presented approach allows for designing and fabricating single mode couplers in an efficient and simple manner.

Multimode fiber (MMF) regarded as an excellent choice for providing large capacity and high-speed for applications such as data centers due to its adaptability and unwavering quality. The ceaseless development and the increase of Internet users that emphasis on increasing data capacity have promoted mode division multiplexing (MDM) as a promising contender for providing further level of multiplexing freedom by propagating several and dissimilar channels in different mode stream. This paper investigates and analyzes the effects of launching MDM spot mode with various vortex order using vertical-cavity surface-emitting laser array in conjunction with equalization scheme. A capacity of 40 Gbit/s transmitted over MMF long distance of 1500 m has been achieved at a wavelength of 1550.12 nm.