Demonstration of a Fourth-Order Pole-Zero Optical Filter Integrated Using CMOS Processes

We demonstrate a compact fully tunable narrowband fourth-order pole-zero optical filter that is fabricated in a silicon complementary-metal-oxide-semiconductor foundry. The filter is implemented using silicon on oxide channel waveguides and consists of a Mach-Zehnder interferometer with two ring resonator all-pass filters (APFs) on each arm. The filter architecture is based on the sum and difference of the APFs responses. The ring resonators introduce a nonlinear phase response in each arm that allows carving narrow frequency bands out of a broad spectrum. In this paper, we demonstrate a 3-dB filter bandwidth of 1.0 GHz with a stopband rejection of better than 25 dB. The filter free spectral range is 16.5 GHz. Thermooptic phase shifters are used to tune the filter. As silicon has a large thermooptic coefficient compared to silica, the demonstrated filter requires a low tuning power of less than 300 mW. In addition, this filter is compact with dimensions 25 times smaller than the same filter would be if it were made using standard silica on silicon waveguides with a 0.8% step index contrast     

Synthesis of Optical Filters Using Sagnac Interferometer in Ring Resonator

We propose a new synthesis method for the implementation of infinite impulse response filters, using a Sagnac interferometer within a ring resonator. This structure permits the synthesis of second-order optical functions per stage. We present the parameters of the structure, which are related to the poles position, radial and azimuthal, and the design procedure, with an example of an autorregresive filter.     

Four-channel switched microwave filter based on optical ring resonators

A four-channel switched microwave filter was demonstrated incorporating a switched optical resonator, which is constructed by integrating a 1 x 4 space switch with arrayed ring filters featuring different free spectral ranges. The four channels centred at 10, 16, 18 and 20 GHz were individually selected to provide a bandpass filtering via the control voltage applied to the switched resonator.     

Synthesis of grating lattice circuits

The realization of high-performance components based on optical infinite impulse response (IIR) filter design theory is desirable for next-generation global optical networks. Previously proposed IIR filter synthesis methods are matrix factorization techniques for a lattice circuit using ring resonators. The size of ring resonator limits the bandwidth of the lattice filters. In this paper, two configurations of grating lattice filters are synthesized by using a scattering matrix representation for the grating. The grating is one of the most powerful optical elements both in fiber optics and photonic integrated circuits. One configuration is a serial grating lattice filter configuration and the other is a parallel grating lattice filter configuration. The actual frequency response of the synthesized grating lattice filter is calculated to show the design limitation due to the frequency response of the element gratings     

Effects of Resonator Loss on Output Characteristics of Ring Microresonator Filter

The ring microresonator filter considering resonator inner loss is analyzed theoretically, which has one input port and two output ports, Some universal relations for coupling of optical power between microresonator and dielectric waveguides are presented. The analytical expressions of filter bandwidth or the full width at half maximum （FWHM）, free spectral range and finesse of resonator are derived. The characteristics of the ring microresonator filter are discussed numerically. It is demonstrated that the loss of the ring resonator reduces the peak value of transmission, widens the filter bandwidth, and reduces the finesse of the resonator filter.     

一种新颖的复合环形谐振腔的理论分析

文章基于环形谐振腔所具有的非线性相位传输特性,提出了一种新型的动态光谱滤波器结构,它将全通环形谐振腔调相器接入平衡马赫-曾德干涉仪,实现复合结构的动态滤波特性.与传统的马赫-曾德干涉仪相比,此复合滤波结构可利用远小于π的相移调整实现输入光信号的开关,因此,在提高开关速度、降低调相器功耗等方面具有重要的应用价值.     

The realization of all-pass filters for third-order dispersioncompensation in ultrafast optical fiber transmission systems

Thin film (TF)-based coupled cavity all-pass filters (CCAP) have the potential for providing compact, low-loss, and highly stable third-order dispersion (TOD) compensation in ultrafast optical fiber transmission systems employing optical time-division multiplexing (OTDM). In this paper, a methodology for designing CCAP filters for TOD compensation is presented, First, we develop a theory necessary for designing the cavity structure, that is, mirror reflectivity and cavity spacing, of CCAP filters. As a next step, we discuss how we can represent such filters as TF devices and demonstrate several TF-layer design examples. Finally, a coupled two-cavity filter is constructed and tested. The filter has a center wavelength that can be varied over a range of 8 nm and can compensate for fiber TOD between 2.0 and 15.5 ps ³ over a bandwidth between 3.6 and 1.2 nm, respectively. The peak spectral ripple of the filter is 1.0 dB, The experimentally measured dispersion curves of the filter agree well with the theory     

A reduced-size dual-mode bandpass filter with capacitively loaded open-loop arms

A novel type of dual-mode microstrip bandpass filter using degenerate modes of a dual-mode microstrip square loop resonator with capacitively loaded open-loop arms is proposed. Such a dual-mode bandpass filter with a 0.75% bandwidth at the center frequency of 1.603 GHz is designed and fabricated to demonstrate the design of reduced-size microstrip filters. It is shown that the proposed filter has a size reduction of about 59% at the same center frequency, as compared with the dual-mode bandpass filters such as microstrip patch, cross-slotted patch, square loop and ring resonator filter.     

Tunable filters based on an SOI nano-wire waveguide micro ring resonator

Micro ring resonator(MRR) filters based on a silicon on insulator(SOI) nanowire waveguide are fabricated by electron beam photolithography(EBL) and inductive coupled plasma(ICP) etching technology.The cross-section size of the strip waveguides is 450×220 nm2,and the bending radius of the micro ring is around 5μm.The test results from the tunable filter based on a single ring show that the free spectral range(FSR) is 16.8 nm and the extinction ratio(ER) around the wavelength 1550 nm is 18.1 dB.After thermal tuning,the filter’s tuning bandwidth reaches 4.8 nm with a tuning efficiency of 0.12 nm/℃Meanwhile,we fabricated and studied multi-channel filters based on a single ring and a double ring.After measurement,we drew the following conclusions: during the signal transmission of multi-channel filters,crosstalk exists mainly among different transmission channels and are fairly distinct when there are signals input to add ports.     

Coupled-waveguide exchange-Bragg resonator filters: coupled-modeanalysis with loss and gain

Novel resonator filters made of two closely coupled asymmetric waveguides with phase-shifted exchange-Bragg grating, are investigated. Coupled-mode theory based on the normal modes is used to examine the effects of loss and gain on the filter spectral responses. The filter exhibits a total transmission at central wavelength and a rejection to the adjacent waveguide with high extinction ratio for other signals in the absence of loss and gain. Material loss reduces the transmitted power level and increases the filter bandwidth. With a certain amount of optical gain, good transmission can still be maintained in the presence of material loss. Proper control of the optical gain can lead to the amplification of both the transmitted and reflected powers at the central wavelength