Silica-based PLC optical splitters are widely used in commercial optical access network, PDS-based FTTH system, for distributing and combining optical signals to end-users. They offer not only high optical performance such as low insertion loss, low polarization dependent loss, and wavelength flatness, but also compactness in size, low cost, high reproducibility and long-term reliability. Since optical splitter is a key component in optical access network, it is necessary to ensure its reliability sufficient to operate for a lifetime of more than 20 years. Telcordia GR-1209-CORE and GR-1221-CORE are two commonly referred standards which are used to evaluate the reliability performance of an optical device under test. They are conducted in form of a series of tests under specific environmental conditions such as temperature, humility, pressure, etc. If a device can maintain its claimed specifications during or after the tests, we have confidence that it should robust enough to stand against severe environmental conditions for more than 20 years. Otherwise, failure analysis should be carried out to remedy the problems. In this thesis, factors which lead to the failure of PLC optical splitters during Telcordia Tests will be studied both experimentally and theoretically The study is divided into two main parts. The first part is on the failure analysis of fiber array, which is a key component used to couple the 10 ports of PLC chips with fibers for ease of use. In the assembly of fiber arrays, a number of fibers, usually in number of 8, 16 32 etc, are placed on an arrays of V-grooves with spacing up to sub-micron positioning accuracy. Then a cover lid is placed on top of the fibers and bonded using UV adhesive. We find that one main factor, which causes the fiber arrays failed in the testing is due the weak or non-uniform adhesion between the material interfaces. As a result, it leads to fibers misalignment and lid detachment when go through reliability tests. This issue has been tackled in three ways: the control of UV exposure pattern to the adhesive, the choice of suitable adhesive materials, and through the plasma surface treatment to enhance the surface adhesion. Some samples are fabricated to verify our study. These samples are all pass in the Telcordia Tests and are used in the assembly of PLC optical splitter. The second part of our study is on the effects of CTE mismatch to the reliability of packaged PLC optical splitters. Since a packaged PLC splitter composed of many materials with different CTE, these CTE mismatch would induce different dimensions of elongations or contractions in material bonding interfaces when experiencing temperature variation. Hence, the thermal stress or strain built-up within the package will critically influence the stability of optical performance. We apply thermal cycling test in order to study the correlation between CTE mismatch effect and optical performance. Based on the study, a modified packaging design aims to minimize the problem is proposed. Some samples are packaged based on the new design, which are all passed the Telcordia Tests showing that they have sufficient durability and reliability for use in commercial optical access network application. We find that all our study is not only applicable to PLC splitters but also applicable to the packaging of other PLC chips devices.