Chapter 1 Introduction
The lightwave technologies are very important for the applications of optical communication systems [1-2]. Using lightwave technologies for analyzing reflection/transmission frequency responses of optical components is a great issue nowadays [3-4]. For those reasons, we designed a novel two-way optical frequency domain reflection/transmission system for the measurement of optical components and systems in this thesis.
Recently, the applications of photonic bandgap (PBG) have a great development in coplanar waveguide (CPW) microwave filters [5-12]. The PBG is a periodic structure which can be applied for rejecting the unexpected band. CPW filter has many advantages compared to other ones, such as wider ranges of realizable impedance values, small dispersion, simple realization of series and shunt circuit elements, and easy integration with lumped-elements and active devices [13-15]. According to the PBG and CPW concepts, we propose a PBG-CPW frequency division multiplexer (FDM).
A 1x2 microstrip FDM with two output frequencies, 700 MHz to 1950 MHz and 2100 MHz to 3000 MHz, was
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proposed in 1999 [16]. In 2002, a 1x3 FDM was realized by connecting three directional filters in series, where the directional filters were designed for center frequencies of 1.472 GHz, 2.944 GHz and 4.416 GHz [17]. The FDM is fabricated on FR4 glass-epoxy single side board and it is used to divide the broad band microwave signals generated from network analyzer into three different passband outputs.
Oppositely, the FDM can collect microwave frequencies from the three different passband inputs into one common output.
In other words, the FDM can be treated as multiplexer and de-multiplexer.
A broadband two-way electrooptic probe with operation frequency from 0.3 GHz to 3.0 GHz has been proposed for optical component network analyzer [18]. Electrooptic probe is a device which is combined by microwave components and optical components. In our thesis, we used three proposed FDMs and three microwave circulators to establish the electrical probe which is the electrical part of electrooptic probe. Besides, an optical transmitter, an optical receiver, and an optical circulator are used for the optical part of electrooptic probe.
The research in measuring the wavelength and frequency response of fiber Bragg grating (FBG) and chirped fiber Bragg grating (CFBG) is a great issue today [19-23]. A FBG can reflect a predicted narrow or broad range of wavelengths of light incident on the grating, while passing all other
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wavelengths of the light [24-25].
In chapter 2, we designed a novel CPW FDM using PBG cell combination concepts. The output frequency bands of this FDM include three different ranges. In other words, this FDM component can be more widely and flexibly applied in microwave communication system. The theories and experimental results of our proposed FDM will be exhibited in this chapter.
In chapter 3, we develop a novel two-way electrooptic probe which is combined by microwave components and optical components. Then, we report the probe with describing each component and analyzing their experimental results. The theoretical model of microwave circulator has also been derived in detail. Finally, the experimental results of electrical probe and electrooptic probe have been discussed in this chapter.
The Through-Reflect-Line (TRL) calibration method is applied in measuring the optical device under test (DUT) of the two-way optical frequency domain reflection/
transmission system which will be proposed in chapter 4.
In chapter 4, we use two electrooptic probes, which have been designed in chapter 3, to achieve a two-way optical frequency domain reflection/transmission system. We used a FBG and a CFBG as the optical DUT in conventional optical network analyzer and our proposed two-way optical frequency domain reflection/transmission system. We also
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measure frequency responses of FBG and CFBG, respectively.
Then analyzing the experimental results of these two types of FBG in this chapter.
At last, the conclusion is given in chapter 5.
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