In this paper, a three ringresonator serially coupled is considered as an optical filter. We are going to improve the performance of the designed optical filter by increasing the quality factor and finesse of filtered wavelengths. The first and last rings are coupled to the bus waveguides that carry the input and output fields. The effect of coupling parameters and ring radii on the filtering of operating wavelengths which are between 1545-1550 nm with narrow Free Spectral Range (FSR) less than 0. 5 nm is investigated. Using the transfer matrix method, all the rotating and output fields are obtained. FSR, Full Width at Half Maximum (FWHM) and Finesse (F) are evaluated by the wavelength response plots of the output ports obtained in Wolfram Mathematica. The behavior of structure is analyzed by a new approach in order to filter the resonant wavelengths of the transmission channel with higher finesse.

In this paper, we proposed a novel structure for designing all optical filter based on photonic crystal structure. In designing the proposed filter, we simply employed a point defect localized between input and output waveguides as wavelength selecting part of the filter. The initial form of this filter is capable of selecting optical waves at l=1560 nm, the transmission efficiency of the filter is 100%. In designing and studying the optical properties of the filter, we used plane wave expansion and finite difference time domain methods. After designing the filter, we studied the impact of different parameters on the filtering behavior of the structure. The total footprint of the filter is less than 100 100 mm2. Simplicity of design and ultra-compact dimensions are the most significant characteristics of our filter.

In this paper, a new design of optical channel drop filter based on two-dimensional photonic crystal ring resonators with triangular lattice is proposed. The rods of this structure is silicon with the refractive index 3. 46 and the surrounding environment is air with the refractive index of 1. The widest photonic band gap obtained is for filling ratio of r/a = 0. 2. The filter’ s transmission spectrum is calculated using the two-dimensional (2D) finite-difference time-domain (2D-FDTD) numerical method. The simulation shows 100% dropping efficiency and suitable quality factor at 1519. 4 nm wavelength achieved for this filter. Also, in this paper, we investigate parameters which have an effect on resonant wavelength and transmission spectrum in this CDF, such as refractive index of inner rods and whole of dielectric rods of the structure. The overall size of the structure is small that is 14 μ m × 14μ m which is suitable for photonic integrated circuits (PIC) and optical communication network applications.

In this article, we present new research on the impact of various optical filters on the functionality of an orthogonal Optical Frequency Division Duplexing (OFDM) system for the first time. This paper focused on long-haul optical systems using four Quadrature Amplitude Modulation (4-QAM) methods for OFDM systems. The analysis demonstrates the impact of choosing a Gaussian, Rectangular, or Trapezoidal optical Filter on the effectiveness of the optical system used for long-distance high data rate transmission. Compared with other systems for long-distance transmission using various filter types, 4-QAM OFDM showed a high Bit Error Rate (BER) performance. Significant findings like transmitting Power received Power, and Error Vector Magnitude (EVM) is compared with the system's propagation length.

In this paper, an optical filter based on a two dimensional photonic crystalring resonator (PCRR) with triangular lattice is designed and presented. For thispurpose, the effects of positioning, arrangement and the number of the inner rods of thedual-curved PCRR on the performance characteristics of our optical filter such as thetransmission coefficient and the quality factor have been fully investigated. Calculationresults show that a transmission coefficient of 100% with a quality factor of 2400 at theoperating wavelength of nearly 1576 nm can be achieved. The proposed optical filtercomparatively performs better than the previously reported ones. In addition, thisstructure can be used for the design of optical multi-channel demultiplexer. To study thephotonic band gap of our structure, the plane wave expansion (PWE) method has beenused and the finite-difference time-domain (FDTD) method has also been employed toanalyze the optical behavior of the proposed device.

In this paper, Using a 2D photonic crystal and a novel square ring resonator, several compact and simple structures have been introduced in the present paper to construct optical add/drop filters and multi-channel filter. The difference structures has been designed and simulated by using the proposed square ring resonator and different dropping waveguides. To do analyses, the finite-difference time-domain method and the plane wave expansion have been used. The three add/drop filters can separate the wavelength of 1554 nm with a transmission coefficient of 100 %, quality factor of 1295 and bandwidth of 1. 2 nm. The models of structures are simulated by the RSOFT CADLayout software. The results, flexibility and simplicity of structures have caused from their used to designing of an optical multi-channel filter with a channel spacing of 1. 5 nm. The advantages of this design include the channel spacing, quality factor, transmission coefficient and bandwidth which are suitable for applicability in optical communication systems such as wavelength division multiplexing systems.

In this paper, an optical filter based on a two dimensional photonic crystal ring resonator (PCRR) with triangular lattice is designed and presented. For this purpose, the effects of positioning, arrangement and the number of the inner rods of the dual-curved PCRR on the performance characteristics of our optical filter such as the transmission coefficient and the quality factor have been fully investigated. Calculation results show that a transmission coefficient of 100% with a quality factor of 2400 at the operating wavelength of nearly 1576 nm can be achieved. The proposed optical filter comparatively performs better than the previously reported ones. In addition, this structure can be used for the design of optical multi-channel de multiplexer. To study the photonic band gap of our structure, the plane wave expansion (PWE) method has been used and the finite-difference time-domain (FDTD) method has also been employed to analyze the optical behavior of the proposed device.