Performance Analysis of Phase-coding Based on Superstructured Fiber Bragg Grating

We experimentally demonstrate a record 4096 (=16 × 16 × 16)-ary optical code division multiplexing (OCDM) system at 2.5 Gbps using multidimensional phase shift keying (PSK) codes generated/processed by a single multiport optical encoder/decoder (E/D). To analyze the system performance, we evaluate the power margin and the data confidentiality. For application to access networks, we propose and numerically evaluate the performance of 10 Gbps, 4096-ary optical code division multiple access (OCDMA)-based passive optical network (PON).

The frequency response of a microwave photonic filter using superstructured fiber Bragg grating, and dispersive fiber is analyzed theoretically and experimentally. The results indicate that the source spectral bandwidth introduces additional power penalty.

Broadcast-and-select optical code division multiplexing (OCDM) and a WDM hybrid network are presented, in which 10 Gbit/s spectrum-sliced supercontinuum (SC) binary phase shift keying (BPSK) pulse code sequences are used as multi-wavelength optical BPSK code sources.

Chapter 2 - Light-Guiding Fundamentals and Fiber Design

Wavelength dispersion characteristics of single-mode silica fibers in a very low-loss region, including zero dispersion wavelengths, are studied in detail using a "difference method." Wavelength dispersion of single-mode fibers is compared for fibers with same material dispersion but with different waveguide structure. Material dispersion is evaluated by extracting waveguide dispersion from experimental results. Effects of waveguide dispersion on the zero dispersion wavelength of the single-mode fiber in a longer wavelength region are clearly analyzed. Single-mode fiber design consideration is given from the wavelength dispersion point of view.

The impact on the performance of the direct-sequence optical code-division multiple-access (DS-OCDMA) system due to wavelength mismatch between encoder and decoder is investigated. Simulation results show that the encoder-decoder wavelength mismatch will degrade the bit-error-rate performance of the DS-OCDMA system drastically by decreasing the contrast ratio of the correctly and incorrectly decoded signals and lower data rate systems are more vulnerable to wavelength mismatch than higher data rate systems. In practical DS-OCDMA systems, the wavelength mismatch between encoder and decoder should be minimized, and some protective measures, such as temperature stabilization and fiber Bragg grating (FBG) packaging, should be taken to enhance the immunity of the superstructured FBG encoder/decoder to ambient conditions.

Impact of channel-spacing on next 400 Gb/s Ethernet 40-km PMD based on [formula omitted] WDM architecture

A single-mode Te-rich chalcogenide (ChG) fiber for mid-infrared has been fabricated via an isolated extrusion method. The optical loss of the fiber is 3-4 dB/m in a range of 6.5-10.5 µm. Mid-infrared (MIR) supercontinuum (SC) generations were experimentally investigated in the step-index single-mode fiber with femtosecond laser pulse from an optical parametric amplifier (OPA). By pumping 17 cm-long fiber at 5 µm and 8 µm, the spectra spanning from 1.8 to 15 µm and 2.3 to 14.5 µm, respectively, were observed. The results show that the efficiency of SC generation is highest by pumping at near zero dispersion wavelength in single-mode fiber. It reveals that the superiority of single-mode fiber in SC generation over multimode is the elimination of high-order modes (HOMs) interaction. Besides, a repeat SC experiment was carried out for fiber stability test after half a year.

Future 4G systems require transmission of richer multimedia services which inevitably implies an increase in data rate. Orthogonal frequency and code division multiplexing (OFCDM) technique has shown promising results in achieving a high data rate while simultaneously combating multipath fading. OFCDM is an amalgamation of orthogonal frequency division multiplexing and two‐dimensional (2D) spreading. 2D spreading helps to achieve diversity gains in both time and frequency domains. The present OFCDM systems employ 1D orthogonal variable spreading factor (OVSF) codes to achieve the required 2D spreading in code multiplexed channels. However, 2D OVSF codes have better correlation properties in comparison to 1D OVSF codes. Motivated by this principle, the authors propose a spreading scheme for OFCDM systems using 2D OVSF codes. The spreading scheme is designed to increase the system throughput and reduce multi‐code interference. Here, the authors study the OFCDM system performance using the proposed spreading scheme in a multipath fast fading channel with varying spreading factors in both time and frequency domains. The results are compared with the existing OFCDM systems using 1D OVSF codes.

Linearization of an intensity-modulated analog photonic link using an FBG and a dispersive fiber

Currently, communication systems are widely used, where optical fiber is used as a transmission medium. In turn, decision and control of optical fiber parameters has become needfull, since these parameters have a significant impact on the quality and quantity of transmitted information using fiber-optic communication systems. One of these parameters is cut-off wavelength of the single-mode optical fiber, which determines the minimum wavelength of optical radiation at which the optical fiber supports only one propagated mode, in other words, operates in single-mode. The problem of decision cut-off wavelength of the optical fiber used in fiber-optic communication systems is quite relevant and demand, since when the optical fiber operates in multimode, its throughput decreases due to inter-mode dispersion. The article describes methods for measuring cut-off wavelength of the optical fiber. Variant of a high- precision apparatus for measuring cut-off wavelength of the optical fiber has been proposed and tested. The measurements were performed based on the reference bending technique described in GOST R IEC 60793-1-44-2013. The analysis of the accuracy characteristics of the developed apparatus is made, a quantitative assessment of the measurement error is obtained.

The chromatic dispersion (CD) of a single mode fibre (SMF) is an important issue in a long haul optical communication system when the new generation of optical system is introduced operating at the wavelength of 1.55 /spl mu/m with the bit rate of 10 Gb/s. The CD effect will result in pulse spreading and causes inter-symbol interference (ISI). This paper proposes a promising technique to compensate CD by using an optical all pass filter (OAPF) as an equaliser. The phase response of OAPF will be designed to equalise the phase delay of SMF which is the main cause of CD. The simulation of the mathematical model of the optical system at 10 Gb/s employing the proposed OAPF will be presented. A minimum mean square error technique was used to optimise the equaliser and the simulation results show the pulse spread improvement of 33% and fully compensated were achieved at full-width half-maximum (FWHM) for 100 and 160 km of SMF. respectively. The eye diagram also shows an improvement of 32 dB in dispersion penalty when OAPF equaliser is used at a distance of 160 km.

The measurement of chromatic dispersion in single-mode fibres using a 1300 nm edge-emitting LED, a 1550 nm laser diode, and the phase shift method are described. The approach is insensitive to fibre temperature change throughout the measurement, and may enable dispersion in single-mode fibre optimised for 1300 nm operation to be characterised in the 1550 nm region, as well as in the 1300 nm region. The influence of the edge-emitting LED on the measurement is also considered, in that error can arise through selecting narrow wavelength regions of its output, and matching its wavelength coverage to the fibre zero dispersion region is important for long length characterisation. Measurements on installed SM fibres are discussed.

In this paper, we compare the nonlinearity effects of single mode fiber (SMF) and non-zero dispersion shifted fiber (NZ-DSF) on the performance of optical coherent transmission systems. We estimate the nonlinearity effects of fiber, referred to as nonlinear interference noise (NLIN), by using the so-called enhanced Gaussian noise (EGN) model, and compute signal to noise ration (SNR) of optical coherent transmission system by considering NLIN and optical amplifier noise, referred to as amplified spontaneous emission (ASE) noise. By considering EGN model we optimize the lunch power of optical coherent systems considering SMF and NZ-DSF. Finally, a 100Gbps optical coherent transmission system is simulated and its results are compared with analytical results obtained based on the EGN model. The closeness between analytical and simulation results reveal the accuracy of the EGN model and the power optimization formulations.

This paper presents a modification in conventional asymmetrically clipped optical OFDM (ACO-OFDM) frame for direct detection intensity modulation (DD-IM) system. Proposed dual frame OFDM consists of two similar frames and transmitted with optical phase conjugation for dispersion and non-linearity mitigation in optical fiber. Proposed system is compared with another scheme- phase conjugated sub-carrier coding (PCSC) in OFDM. Authors have compared the proposed system performance with PCSC for single mode fiber (SMF) with length 10 km and multi-mode fiber (MMF) with length 100 meters. Simulation results show that PCSC scheme performs better for SMF but in case of MMF, performance of proposed system is better.