A series of service-affecting field failures in cold weather (−40°C to 0°C) initially and in more moderate conditions (up to 15° C) recently have raised concerns about the temperaturedependent transmission performance of loose tube fiber optic cables. The first field failures occurred in 1550-nm aerial transmission lines while more recent failures have affected 1310-nm operations. Field analyses and laboratory temperature-cycling measurements of the affected cables established that the transmission loss resulted from fiber microbending due to random fiber contacts with the buffer tube walls caused by the axial shrinkage of the buffer tubes relative to the cable central member. High resolution thermal expansion/contraction measurements on commonly used PBT (Polybutylene Terephthalate) and PP (Polypropylene) buffer tubes indicated that the total axial shrinkage consists of two components: irreversible shrinkage due to the relaxation of processing-induced stresses and reversible thermal contraction/expansion. The magnitude of both components depends strongly on the buffer tube material and the processing conditions used to manufacture buffer tubes. In this report, we review our work to date in developing field installation and cable design solutions, present a comparison of two buffer tube materials, identify key materials issues that determine buffer tube dimensional stability, and discuss the implications of these issues on the field installation and cable design solutions that we have developed to minimize the risk of low-temperature transmission loss in loose tube cables.

We describe the results of accelerated lifetests performed on silica-based planar lightwave circuit (PLC) devices. Specifically, we tested PLC splitter modules in damp heat environments with different temperatures and humidities. The time-to-failure data of the splitter samples were analyzed by using the Weibull distribution, and the shape parameter was derived as 1.77. Moreover, the temperature and humidity dependence of the median life e was analyzed by using the equation

and the coefficients E and n were determined to be 1.49 eV and 3.70, respectively. The thirtyyear hazard rate is estimated to be less than 40 FIT for PLC splitter modules operating at 60°C/ 40% RH.

Increasing demands for LiNbO3 (LN) optical waveguide devices installed into submarine and terrestrial fiber communication systems necessitate that high quality and long-term reliability (over 20 years) be established. In addition to general requirements for reliability in electrooptical devices, the LN devices need to assure of the dc-drift phenomena in the optical output signal. The dc-drift is caused by the complex electrical nature of constituent device materials; i.e. LN substrates and SiO2 buffer layers on LN. Results of theoretical and experimental investigations of the suppression of dc-drift are applied to the design of practical LN devices, and the devices have been in service for 4 years, as of this moment, without any failure. Here, problems on the dc-drift are discussed from the viewpoints of device reliability and actual fabrication processes.

The aim of the study is to discuss the most general aspects of semiconductor devices durability and reliability. The life time of a semiconductor device is related to the defect structure evolution of the crystalline and noncrystalline components involved. The driving force for the evolution of defect device structure is associated with relaxation processes of internal mechanical stresses. In this report the degradational effects in LEDs based on GaAs(Si) have been analyzed. The discussion of the necessity for research on composite materials creation is also included.

Silicon platforms were fabricated for optical modules and realize sub-micron precision using self-alignment process. This paper features a self-alignment process and use of precision platforms.

Our studies of device lifetime and the main degradation mechanisms in Nichia blue LEDs date back to Spring 1994. Following the initial studies of rapid failures under high current electrical pulses, where metal migration was identified as the cause of degradation, we have placed a number of Nichia NLPB-500 LEDs on a series of life tests. The first test ran for 1000 hours under normal operating conditions (20 mA at 23 °C). As no noticeable degradation was observed, the second room temperature test was performed with the same devices but with a range of currents between 20 and 70 mA. After 1600 hours, some degradation in output intensity was observed in devices driven at 60 and 70 mA, but it was still less than 20%. The subsequent tests included stepping up the temperature by 10 °C in 500 h intervals up to a final temperature of 95 °C using the same currents applied in the second test. This work reviews the failure analysis that was performed on the degraded devices and the degradation mechanisms that were identified.

Long-period gratings were written in nitrogen-doped-silica-core optical fibers by point heating. The periodic variations of the effective refractive index were induced via diffusion of nitrogen from the fiber core. It is shown experimentally that such gratings remain functional at temperatures of up to 1200 °C.

Fiber reinforced structural elements equipped with optical fiber sensors are of potential interest for long term surveillance of bridges, dams, and other civil engineering applications. We report herein on the embedding of optical fiber Bragg grating sensors into continuously pultruded glass fiber reinforced epoxy material (GFRP) rods used as structural elements.

Two fibers, one with acrylic, one with polyimide coating, and fiber Bragg gratings were extensively characterized. The residual axial strain after embedding was measured. Temperature and strain coefficients of Bragg gratings during quasi-static cycling and temperature cycling tests were monitored and compared to extensometric and resistance strain gauge measurements.

The effect of fiber embedding was also studied with push-out tests giving information about adhesion properties like surface bond energy, lateral stress, and coefficient of friction.

For sensor purposes long term characteristics of the conversion factor between the measured Bragg grating wavelength and strain or temperature in the specimen have to be known to identify best-suited coatings for embedding and protecting fiber sensors and for obtaining reliability data on sensor performance.

The topic of reliability of UV-induced fiber gratings is reviewed. Approaches to assess and predict changes in optical properties of fiber gratings due to thermal decay of refractive index modulation are presented and compared. The mastercurve/demarcation energy diagram approach is shown to be a powerful and general method for the purpose. The process of thermal stabilization to obtain gratings with superior stability is delineated. It is shown that the mastercurve approach could be used to analyze other reliability problems such as in predicting hydrogen-induced losses in fibers.