Self-healing algorithm for logical mesh connection on ring networks

A self-healing algorithm is proposed for a ring network connected as a logical mesh. It offers good performance in terms of protection line capacity, restoration time, and survivability against multiple failures     

OA&M framework for multiwavelength photonic transport networks

Photonic networks based on wavelength division multiplexing (WDM) and optical path technologies are expected to realize flexible, transparent, and cost-effective transport networks with a large transmission capacity. This paper explores the design framework of photonic transport networks taking into consideration the operation administration and maintenance (OA&M) functions required for the successful introduction of WDM systems based on the optical path concept. From the view point of network maintenance, clear distinction is made between the optical path layer and the optical section layer to facilitate accurate and smooth failure localization. The digital multiplexing span between physical multiplexing interfaces at the end-to-end digital nodes should have the same maintenance span as the corresponding optical path. We argue that cooperative maintenance by OA&M functions at both the digital and optical layers can be a practical way of network supervision. A supervisory (SV) signal transfer method and a configuration that is suitable for the terrestrial trunk network are also indicated. As an example, a practical SV system design methodology and an actual procedure developed for a single channel optical transmission system based on optical in-line amplifiers are introduced. Furthermore, application of the developed SV system and network restoration schemes is discussed for future WDM-based photonic networks. The OA&M aspects introduced will be valuable for creating future photonic network systems     

Nonlinear influence on PM-AM conversion measurement of groupvelocity dispersion in optical fibres

The authors propose a method for measuring the group velocity dispersion, including the polarity, of optical fibre by using a single wavelength light source. The method is based on the interplay between phase modulation-amplitude modulation (PM-AM) conversion and self-phase modulation (SPM)     

A new life extension method for high cycle fatigue using micro-martensitic transformation in an austenitic stainless steel

Most of the conventional strengthening methods for metals and alloys such as work hardening, precipitation hardening, cause a decrease in ductility and are not very effective for cyclic loading. In this study, a new strengthening method, which is effective for high cycle fatigue, has been developed. The intersections of dislocations in a stainless steel are freezed by very fine martensite particles, which are supposed to suppress dislocation motion at low stress amplitudes. Fatigue life in a high cycle regime increased >60 times, and no decrease in ductility was observed in tensile tests, as compared to a work-hardened stainless steel.     

Chlorine auto-doping by chloride vapor phase epitaxial growth of InP

Chlorine auto-doping phenomenon was found for the first time in InP epitaxial growth by using a PCl₃/InP/H₂ system. Chlorine atoms act as a donor in the epitaxial layer and the carrier concentration is dependent on the facet of InP substrate. The carrier concentration of the InP layer on ( 111)B facet was over 10³ times higher than that on (111)A substrate.     

Noise figure monitoring of optical amplifiers via backwardamplified spontaneous emission

A new configuration of an optical amplifier is proposed that provide in-service noise figure (NF) monitoring. It is difficult to determine the NF of traditional optical amplifiers in operation because the amplified spontaneous emission (ASE) power cannot be measured separately from the output signal power. The proposed technique measures the NF from the backward ASE power. The discrepancy between the NF measured from forward ASE (using the traditional technique) and backward ASE (proposed technique) is found to be less than 1.0 dB at input powers below -6.2 dBm. A prototype optical amplifier is successfully used as a linear repeater, in a 10 Gbit/s 200 km transmission experiment     

New measurement method for polarisation dispersion in single-mode fibres employing frequency-modulated optical signal

A new measurement method for polarisation dispersion in a single-mode fibre, utilising the coherence property of frequency-modulated laser diode light, is proposed. Polarisation dispersion is determined exactly by selecting the modulation condition which gives depolarisation light at the fibre end.     

Route diversity with hitless path switching

A route diversity `hitless' protection switching scheme is proposed that is free from hit loss even for unpredictable system failures. Freely switching between the working and protection paths improves the signal quality at the system output because the system automatically selects the no-error frame     

Supervisory signal transmission by modulating the mB1C codecomplementary bit

A supervisory signal transmission method for digital optical communication systems is proposed. It minimizes circuit scale, clock frequency increase, and interference between traffic and supervisory information, and does not require customization. The supervisory signal is carried by the amplitude-modulated complementary bit in the mB1C coded sequence. The code adds a single bit after every m bit block as a complement to the last bit of the block. Clock frequency increase is kept at a level of (m+1)/m. This additional bit is called the C bit. If the C bit's amplitude is modulated according to the supervisory (SV) signal and the main data block is not modulated, traffic and supervisory information can be isolated in time over the same fiber transmission     

Line terminating multiplexers for SDH optical networks

WDM and TDM systems are compared for the next generation of line terminating multiplexers operating at around 10 Gb/s. A byte-interleaving circuit configuration suitable for large-scale synchronous multiplexing in multiples of eight is proposed. A prototype terminal circuit for STM-64 multiplexing that uses BiCMOS, Si bipolar, and GaAs MESFET IC technologies is reported