Optical Signal Processor Using Electro-Optic Polymer Waveguides

Since the growth of fiber optic communications, extremely low cost optical modules have been expected to be realized. Particularly for the subscriber applications and local area networks (LANs), less than half of past module cost is required. In accordance with the spread of fiber optic transmission, higher volume manufacture is also needed. To attain both of low cost and high productivity, we developed passive alignment technique and optical coupling structure that is suitable for automatic assembly. We also developed automatic assemble equipment for producing several types of optical modules. To reduce optical module cost, it is important to cut down the assembly cost and expensive parts such as optical lens. The passive alignment technique brings us to realize easy assembly of modules and minimize the constructed components of optical coupling. Our mass production techniques include not only for optical coupling but also packaging of the module. We have several types of optical modules according to different fiber communication systems; there are laser modules, detector modules, optical interface modules that are integrated optical coupling and electrical circuit, and PLC (Planar Lightwave Circuit) modules that are integrated passive component. Basically all modules have same optical coupling structure and keep the design rules for automatic assembly. Accordingly, we can use the same equipment for the same assembly process. In this paper, we will introduce basic assembly process and our mass production line for optical coupling and packaging by using passive alignment technique.

We have proposed and demonstrated a band rejection filter based on grating-assisted forward coupling between an electrooptic polymer waveguide and a passive polymer waveguide. A wavelength tuning by the electrooptic effect induced by poling has been also demonstrated.

Besides optical fibers are excellent communication media, they are attractive for real time, high speed signal processing on the ground of that they possess very nice merits such as low-loss, large bandwidth-delay product, light weight, and immunity to electromagnetical interferences. A typical optical fiber signal processing device is composed of light sources, delay lines, attenuators, directional couplers, and photodetectors. Many various functions such as frequency filtering, convolution, pulse compression, high speed pulse generation, encoding, and decoding for the incoherent optical fiber signal processing devices are reported in the literature. Recently the lattice optical fiber structures are investigated intensively due to convenience for mathematical formulation and implementation. Although the optical fiber signal processing devices have many attractive features, they have inherent constraints owing to positive system properties, i.e. nonnegative quantities of signals(optical intensities), attenuations, and coupling coefficients. The constraints of the finite impulse response (FIR) optical fiber filters were presented. In this paper, we establish the constraints of the infinite impulse response (IIR) optical fiber filters by means of investigating the possibility of designing the filters with the desirable properties such as maximally flat or equiripple responses. In addition, the characteristics and design principles of the optical fiber filters can be clearly understood from the processes. The mathematical derivation makes use of the state-variable analysis technique to approach this problem. This technology is suitable to describe for both cases: FIR and IIR. Hence the confirmed constraints can be directly applied to the FIR case.

Summary form only given. The author discusses developments in optical signal processing and highlights the many ways in which the technology of optical and electronic signal processing is converging.

In the last few years, a considerable effort has been expended on the development of a number of both active and passive guided-wave devices, such as laser diodes, electrooptic modulators, acoustooptic transducers, photodetectors and microlens arrays, for optical signal processing applications including optical computing 1-3. Many simple optical devices can be easily fabricated by using mature and reproducible technologies. The interest in optical processors involving simple devices is mainly due to a lower power consumption, reduced size, cost and weight and high throughput with respect to the corresponding electronic processors. A number of guided-wave optical circuits for communications, signal processing and optical computing have been demonstrated using the acoustooptic, magnetooptic and electrooptic effects 4. Moreover, fields of application of particular interest are synthetic aperture radar (SAR), remote sensing and beam forming of linear array antennas, which are all well suited for optics-based processing because of the parallel processing allowed by optical architectures. Therefore, guided-wave optical processors can be successfully applied to the optical control of microwaves, to the reconstruction of two-dimensional images using both spatial and time integration, to data classification and identification in satellite applications and for performing a number of signal processing and optical computing functions.

We have already proposed a Gigabit Ethernet-Optical Switched Access Network (GE-OSAN) architecture that realizes longer transmission distances and achieves higher security than the conventional Passive Optical Network (PON). To confirm the technical feasibility of the architecture, we introduce here a GE-OSAN prototype system for down-stream transmission. We present the Optical Switching Module (OSM), which uses (Pb,La)(Zr,Ti)O3 (PLZT) optical packet switches, and show that it realizes switching within 10ns of the designed position in the Inter-Frame Gap (IFG). We also introduce an Optical Network Unit (ONU) with optical burst receiver that uses off-the-shelf commercial devices to reduce its cost; two types of an optical to electrical signal (O/E) converter are implemented for performance comparison. After testing both of them, we select the one that satisfies our acquisition time requirement of 64ns.

An optical crossbar interconnected signal processor, proposed previously, is reviewed. The ability to implement difficult -to-parallelize algorithms on this processor with reasonable efficiency is illustrated using optimal least square filtering. An inversefilter for removing the effects of a ringing source from reflected data is used as an example. A large number of Toeplitz matrixequations must be solved to determine the optimum inverse filter length and phase. Efficient parallel computation is required. Equations for Levinson's algorithm are provided and an implementation on the optical system is suggested. Performance estimates suggest that interleaving may be used to improve efficiency from 5% to approximately 30 %. Introduction An optical crossbar interconnected signal processor was proposed previously that has a large number of processing element.connected via optical fibers to an optical crossbar switch'''. A deformable mirror device is used to construct the crossbar switch.I previously showed how to efficiently implement basic signal processing algorithms such as an FFT, systolic filter, and matrix -

We develop an integrated optical packet and circuit switching node in which signaling via optical packet switching is implemented. We demonstrate 80 (8λ × 10) Gbit/s optical packet switching with <;1E-4 packet-loss-rate, 8-lightpaths establishment, and dynamic wavelength-resources control.

We numerically analyzed the modulation characteristics of an InP organic hybrid (IOH) optical modulator consisting of an InP slot waveguide and an electro-optic (EO) polymer. Since InP has a higher electron mobility and a lower electron-induced free-carrier absorption than Si, the series resistance of an InP slot waveguide can be significantly reduced with relatively smaller optical loss than an Si slot waveguide. As a result, the trade-off between optical loss and modulation bandwidth can be remarkably improved compared with a Si organic hybrid (SOH) optical modulator. When the modulation bandwidth was designed to be 100 GHz, the optical loss of the IOH modulator was 13-fold smaller than that of the SOH one. The simulation of the eye diagram revealed that the improved optical modulation amplitude enabled the clear eye opening with a 100 Gbps non return-to-zero signal using the IOH modulator. The IOH integration is promising for a high-speed modulator with low energy consumption beyond 100 Gbps.

Electro-optical modulator based on lithium niobate notched-ring plasmonic metasurface coated with electro-optical polymer

Optical packet switching (OPS) is being considered as one of the switching technologies for a future optical internet. For contention resolution in an optical packet switching (OPS) system, the wavelength dimension is generally used in combination with a fibre delay line (FDL) buffer. In this study, the authors propose to reduce the number of tunable wavelength converters (TWCs) by sharing TWCs for cost-effective design of an asynchronous OPS system with a shared or an output FDL buffer. Asynchronous and variable-length packets are considered in the OPS system design. To investigate the number of TWCs needed for the OPS system, an algorithm is proposed, which searches for an available TWC and an unused internal wavelength, as well as an outgoing channel. This algorithm is applied to an OPS system with a shared or an output FDL buffer. Also, the number of internal wavelengths (i.e. the conversion range of the TWC) needed for an asynchronous OPS system is presented for cost reduction of the OPS system.

We present the design of a 2&times;2 photonic switch operating at 1.55-&mu;m wavelength using electro-optic (EO) polymer waveguides. A Mach-Zehnder interferometer (MZI) is used to implement the proposed switch in which two identical 2&times;2 multimode interference (MMI) couplers are connected by two identical parallel single mode waveguides (two MZI arms). These two single-mode waveguides with electrodes allow modulating the phase difference between the two MZI arms based on the EO effect. In the proposed switch, the EO polymer, IPC-E/polysulfone, is used for the core layer of optical waveguides. UV15 and NOA61 are employed for the lower and upper cladding layers, respectively. The singlemode waveguide structure and 2&times;2 MMI coupler have been designed and analyzed for the EO switch. Device performance has been simulated using the beam propagation method. It is found that the switch performance is most sensitive to the MMI width and less sensitive to the MMI length. Optimized structure has been obtained for the 2&times;2 polymeric EO switch, which has a crosstalk level better than -25 dB and insertion loss lower than -1.8 dB. This performance makes the switch a potential candidate for practical use in photonic systems.

We present a summary of our recent work on using lattice-form Mach-Zehnder interferometers implemented using silica-based planar lightwave circuit technology for optical signal processing. In particular, we demonstrate that the same device structure (either based on 6 taps or 12 taps) can be used to perform various signal processing functions ranging from pulse repetition rate multiplication to arbitrary waveform generation.

In the era of vigorous development of optoelectronic technology, the high-performance lithium niobate optical beam splitter, as a core component for optical signal processing and transmission, provides an excellent material basis for optical signal modulation with its outstanding electro-optical properties. At present, it has been found in research and application that three-dimensional ridge-shaped strip waveguides can enhance the interaction between light and electric fields. Multimode interferometric couplers (MMI) have the advantages of compact structure, simple fabrication and stable mode conversion. The combination of the two can achieve efficient optical beam splitting and precise modulation, effectively improving the modulation efficiency. Through theoretical analysis and numerical simulation, the light field distribution, mode characteristics and modulation performance parameters of this structure were deeply studied. The results show that compared with the traditional structure, this design significantly improves the modulation efficiency, and can effectively reduce mode crosstalk at the same time, achieving stable optical signal beam splitting and modulation. This research provides a new approach for the application of lithium niobate beam splitters in high-speed optical communication, optical signal processing and other fields, which is conducive to promoting the development of optoelectronic integrated devices.

The advantages of Optical Packet Switching (OPS) are transparent data transmission and data format, flexible packet control and dynamic resource allocation. It thus can support high-speed transmission of wideband data networks. Unlike Optical Burst Switching (OBS) systems which need reserved channel to transmit destination address, an advanced OPS solution using Optical Orthogonal Code (OOC) label for payload transfer has been proposed in this paper. Different from other OPS systems, our edge nodes are required to realize some special tasks including extracting destination addresses of the received IP packet which is used as payload in our OPS systems and sending the addresses to the OOC label generator. The OOC label will later be used to identify the destination of each payload at the core node for optical switching. Meanwhile, the higher-priority flow can be prior-serviced according to the Type of Service (TOS) in the head of IP packet. It is experimentally shown that the edge nodes in this OPS system can effectively improve the efficiency of packet switching and the speed of data transmission. The edge node implementation contains two parts: the hardware and software. For the hardware part, all necessary modules have been integrated onto one PCB board, thus avoiding possible instability caused by interconnecting different modules like transmitting/receiving Ethernet frame module, Field Programmable Gate Array (FPGA) processing module and optical transceiver module etc. from different Printed Circuit Boards (PCB). For the software part, the whole of system was based on MicroC/OS-II operating systems running on the Nios II soft core processor. It is verified by the experiment that embedded system designed with Nios II soft core CPU can help to speed up the hardware design. With the SOPC Builder's development environment, more attention can be paid to the structure and function of the system without worrying about the details of the circuit design, and better performance on system stability and reliability could be achieved at the same time.