Standard photonic crystal (PC) waveguide gratings show a stopband only in reflection. By incorporating single or multiple phase-shift regions into the PC waveguide gratings, an extremely narrow transmission peak opens up in the reflection band. Using coupled-mode theory together with transfer-matrix formalism, it is shown that by properly choosing the magnitudes of the phase shifts, the transmission spectrum can be tailored into a nearly rectangular line shape. As a specific application, the designed phase-shifted PC waveguide gratings can be used as a filter in dense wavelength-division-multiplexed (DWDM) optical communication systems with a 100-GHz channel spacing. The theoretically calculated results are numerically verified by using two-dimensional (2-D) finite-difference time-domain (FDTD) method.
The work presented in this paper gives performance comparisons of Carrier Suppressed Return-to-Zero Differential Phase-Shift Keying (CSRZ-DPSK) with Return-to-Zero Differential Phase-Shift Keying (RZ-DPSK) against both the effects of Intra-Channel Four-Wave Mixing (IFWM) and inter-channel Four Wave Mixing (FWM) in 16×40 Gb/s WDM systems with symmetrical fiber link schemes. IFWM gives smaller phase perturbation to CSRZ-DPSK signal than to RZ33-DPSK, although BER performance of CSRZ-DPSK is worse than that of RZ33-DPSK. The numerical comparison indicates that RZ33-DPSK is a better candidate for 40 Gb/s WDM systems than CSRZ-DPSK.
Polarization effects such as polarization mode dispersion (PMD) and polarization dependent loss (PDL) have become the critical limiting factors for long haul high bit rate optical fiber transmission. This paper use waveplate models to simulate the statistical performance of optical link with PMD and PDL in 40Gbit/s optical system. Three DPSK modulation formats are compared each other for their tolerance against PMD and PDL. The 33% RZ-DPSK is superior to the other two DPSK formats, the 50% RZ-DPSK and the CSRZ-DPSK whose duty cycle is 67% when only PMD is considered. And in case of PDL, the outages for three DPSK formats do not show obvious changes with the increasing of PDL. Furthermore, the performance of two RZ-DPSK formats, whose duty cycles are 33% and 50% respectively, is superior to that of CSRZ-DPSK. This shows that modulation format with narrower pulse width owns more high tolerance against PMD and PDL, therefore the CSRZ-DPSK format shows poorer performance when it is compared with the other two DPSK formats.
It is important to resolve the questions of how many BIP bytes are required and which EDC should be adopted for performance monitoring in Optical Transport Networks (OTN). Based on the Poisson Error Model and Burst Error Model, we obtain the mathematical expressions for the probabilities of occurrence of a block error and of detecting a block error, as well as the detection efficiency. Analyses and simulations to determine the maximum BER that can be detected (i.e., the saturation BER) and the minimum detection efficiency are given. Conclusions are drawn as follows: one BIP byte per tandem connection monitoring field is adequate for performance monitoring; 2*BIP-4 EDC should be adopted to meet the requirement that the detection efficiency be no less than 90%; 8*BIP-1 EDC is acceptable if the real-time BER measurement estimate is not required.
Atomic functional architecture model has been accepted by ITU-T to describe the functional architecture of transport networks as well as equipment specification in an implementation independent way. With the existing functional architecture components four different solutions have been proposed to model the complex optical channel (OCh) layer network. One approach is to assign 3-R to the OMS/OCh adaptation function; the second approach is to introduce dedicated transparent layers or to split single OCh layer into several sub-layers; the third is to be deployed by using an abstract characteristic information (CI) definition; the last is using super layer architecture component. This paper analyzes these four methods and presents a new approach by introducing virtual layer network and virtual CI. Virtual adaptation, virtual connection point and virtual link connection are also introduced in order to cover the different transparent connections within a layer network. In addition, examples of using virtual layer component to model the OADM with transparent pass-through and to provide the necessary transparent connections for optical network elements are presented in this paper.