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Title: Design and fabrication of integrated polymeric photonics devices for optical communication
Other Titles: Ke yong yu guang tong xun zhi su liao guang ji cheng qi jian de she ji ji zhi zuo
Authors: Chung, Kin Ki (鍾建奇)
Department: Dept. of Electronic Engineering
Degree: Master of Philosophy
Issue Date: 2007
Publisher: City University of Hong Kong
Subjects: Optical communications -- Equipment and supplies
Optoelectronic devices -- Design and construction
Notes: CityU Call Number: TK5103.59.C59 2007
Includes bibliographical references.
Thesis (M.Phil.)--City University of Hong Kong, 2007
xii, 116, 7, 9 leaves : ill. (some col.) ; 30 cm.
Type: Thesis
Abstract: Nowadays, there is tremendous demand in ever-increasing internet bandwidth all over the world. One of the, possibly the best, solution to cater such a demand is through the realization of all optical network system. In such a system, the whole network should be transparent to signals by avoiding the unnecessary optical-to-electrical signal conversion and vice verse. As a result, the full bandwidth of the optical fiber may be fully utilized. Moreover we need a wide range of low-cost, compact, active and passive optical devices to realize such kind of optical network. In this project, we designed and proposed three optical devices, namely, 1) A single electrode operates 22 digital optical switch (DOS), 2) A linear response variable optical attenuator (VOA), and 3)An ultra compact 14 optical power splitter. The first two devices are active devices while the last one is a passive device, which are the basic building blocks of optical network system. The devices are designed based on the operation principle of a wide-angled X-junction and a wide-angled Y-junction structure. As a result, they can be very compact in size and highly integratable. In addition, they were fabricated using polymer materials, which offer a very attractive advantage of low cost at mass production. The key functions and main features of each devices are outlined below. 1) A single electrode operates 22 optical switches In compared with conventional X-junction design, the size of our switch is reduced by six times. This is because the whole design is realized by using only one asymmetric X-junction structure. Another uniqueness of our design is that the switching operation only requires one single electrode. As a result, the control circuitry required to drive this device is much simple than all other existing devices with similar functions. Our switch has a fairly fast rising time, ~100s, which is an order of magnitude faster than that of a conventional thermo-optic device. The average measured crosstalk is less than -20dB. The device finds many applications, such as optical path protection, circuit switching situation, etc. 2) A linear response Variable optical attenuator (VOA) One distinct feature of our VOA in compared with other similar devices is that it offers an excellent linearity over a wide dynamic range of 35dB (TE mode) with fast response (~0.2dB/Sec). Nearly all the existing design of VOAs offer a rather poor linearity and therefore require a much complicated control circuitry in driving the devices. Since our design is based on a similar X-junction structured proposed above, it shares the same advantage of very compact in size, and offering a much higher packing density. Our VOA finds many applications in optical communication system network for power regulation, channel equalization etc. 3) An ultra compact 14 Optical power splitter We have designed a very compact full-pitch 1x4 optical power splitter which is 20 times smaller in size compared with a conventional one. The simulated junction loss is 0.26dB with branching angle of 16. This is the lowest reported value achieved at such a large branching angle. The fabricated device is only 4mm in length with a measured excess loss of less than 1.3dB over entire C-band. Another other advantage of our design is that it only requires two different index materials and can be reproduced at a very low cost using embossing technique. In conclusion, three compact and low-cost polymer optical devices are proposed for the realization of optical network system. They form the fundamental building block of more complicated devices.
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