High-Speed Photonic Functional Circuits Using Electrically Controllable PLZT Waveguides

There is an increasing demand for DWDM systems to support a set of network requirements (span length, total distance, capacity, etc) typically associated with previously distinct network application categories such as access, metro, regional, and long haul. This has led to the development of a multi-haul DWDM system, defined as an agile optical platform, able to combine multiple versions of transponders, amplifiers, and optical add/drop multiplexers (OADM) on the same optical link. The concept of a multi-haul system is applied in a study of DWDM networks that can employ, besides fixed OADM, two types of reconfigurable OADM (ROADM): a two-degree ROADM based on arrayed-waveguide gratings (AWG) and a multi-degree ROADM built with 5x1 wavelength-selective switches (WSS). A cost analysis on a network example calculates the savings obtained if an optimum mix of ROADMs is used on the same DWDM ring instead of deploying one single OADM type at all nodes. A technical feasibility study is performed to validate the performance of a DWDM system with up to 16 ROADMs in a network. To this purpose, OSNR penalties are experimentally determined for AWG and WSS ROADMs due to cascaded bandwidth narrowing, and crosstalk effects, with wavelength detuning values corresponding to locked and unlocked lasers.

A linear tapered double S-shaped arrayed waveguide grating (AWG) was designed as an alternative to a U-shaped AWG, and a complete transmission spectrum for 18 channels of coarse wavelength-division multiplexing (CWDM) was demonstrated. The silicon-on-insulator based AWG with a rib waveguide structure with a broad channel spacing of 20 nm was designed to serve as a multiplexer/demultiplexer. A beam propagation method modeling simulation under transverse electric mode polarization over a free spectrum range of 700 nm was used for the design process. The geometrical dimensions of the AWG rib structure were optimized to achieve the lowest reported insertion loss of 1.07 dB and adjacent crosstalk of −38.83 dB. The influence of different etching depths on the top Si layer of the AWG for a constant core width of 0.6 μm as well as birefringence effects were also investigated. A transmission spectrum response at the output port close to the standard CWDM wavelength grid range of 1271 to 1611 nm with an average channel spacing of 2485 GHz was obtained.

In this study, we design and fabricate an optical interleaver using arrayed waveguide gratings (AWGs). The characteristic of AWGs which is a large channel spacing between two adjacent wavelengths in the same channel, so we can reliably through the tunable fiber Bragg grating (TFBG) to filter. Through the tunable FBG, the reflected wavelength signal, which we want to get, can be sent to the output port. We can also use the optical circulator (OC) to add the wavelength signal from the add port to join the original network routing. This system can also be used to achieve an all-optical multichannel reconfigurable optical Add/Drop multiplexer (ROADM) system.

The development of the Wavelength Switched (WS) Optical Networks (ONet) is introduced to extract the significances of entire Optical Switching (OS) fabrics pertaining to high efficiency and automation. However the selective switches of wavelength (SW) indicates the prior switching elements subjected with Reconfigurable Optical Add/Drop Multiplexers (ROADM) frameworks exhibiting the different color-less, direction-less and also with contention-less (Col-Dl-Conl) switching features. With the implementation of the Col-Dl-Conl based ROADM, the WSw ONet nodes will be asymmetrical subjected to its switching abilities. In the process of Quality of Service (QoS) enhancement, choosing switching abilities plays a major role subjected to number of ports (Np) and the asymmetry depends over SSw port size. This paper introduces an efficient model of ROADM switching connectivity (SwC) to achieve Qos for given Np. The performance analysis is performed by considering QoS and found that it depends on SwC.

A multichannel optical wavelength selective switch is investigated, which can switch signals at arbitrary wavelengths between multichannels in wavelength division multiplexing systems. It is based on the combination of an arrayed-waveguide grating (AWG) multiplexer and an array of optical space-division switches. A monolithically integrated 2/spl times/2 optical wavelength selective switch is successfully fabricated for four multiplexed signals in the 1.55 /spl mu/m wavelength region. Here, an AWG and four 2/spl times/2 thermooptic switches are laid out on a 30/spl times/60 mm/sup 2/ chip. Wavelength selective switching operations for four wavelength signals between two lines are demonstrated in a time slot of 40 ms with a switching speed of 1 ms.

In metro-access optical network, reconfigurable optical add/drop multiplexers (ROADMs) are required. A ROADM based on coarse wavelength division multiplexer (CWDM) and microring resonators (MRRs) has been proposed and demonstrated. The simulation and performance analysis of ROADM system are carried out by using beam propagation method (BPM) and finite-difference time-domain method (FDTD). CWDM based on multimode interference (MMI) principle is designed. A series of MRRs can make up optical switch array with over 28dB switching ratio.

In this paper, we theoretically and experimentally introduce a new reconfigurable optical add/drop multiplexers (ROADM) module which bases on the narrow-band optical switch (NBOS) technology and achieves the narrow-band optical switching with a Fabry-Perot cavity. In comparison with the analysis of the current ROADM technologies, the NBOS-based ROADM module is proven to be cost-effective, low insertion loss, narrow-band, and has a more mature technology. It would grow to be a cost-effective ROADM solution than any of the others.

A compact thermally reconfigurable optical add/drop multiplexer (ROADM) is realized with 500 $\text {nm}\times 220$ nm silicon-on-insulator (SOI) strip waveguides. The demonstrated ROADM has eight channels with a channel spacing of 400 GHz and consists of two identical arrayed-waveguide gratings integrated with eight thermo-optic switches on the same chip. These thermo-optic switches have a broad bandwidth with low loss ( 20 dB) for covering all wavelength channels by utilizing point-symmetric Mach–Zehnder interferometers with bent directional couplers. The ROADM’s footprint is about $770~\mu \text {m}\times 880~\mu \text{m}$ only due to the ultra-strong confinement ability of SOI strip waveguides. The total on-chip loss of the fabricated ROADM is $\sim 15$ and $\sim 7$ dB for the transmitted signals and the added/dropped signals, respectively.

Summary form only given. In optical burst switching (OBS) networks, a short switching time is very important for handling fine grain packets such as TCP ACK packets, which are only 40 bytes in length. At data rate of 10 Gbps, such a data burst will occupy a period of only 32 ns. Therefore OXC (optical cross connector) with fast switching speed, for example < 100 ns, are generally required for OBS networks. There are many methods to configure an OXC. Tunable optical filters may used to build large scale OXC. In an optical filter, the tuning ability is usually achieved by introducing extra phase shift via the electro optic, thermo optic, or piezoelectric effect, etc. Up to date, the most commonly used tunable filter structures are interferometric such as Fabry-Perot (FP) and Mach-Zehnder (MZ) interferometers. They are usually poor in the performance of passband flatness and the crosstalk, and require robust electronics to stabilize the central wavelength. Hence, they are rarely practically used as switching elements in the dense wavelength division multiplexing (DWDM) optical networks. In recent years, digitally tunable optical filter (DTOF) has received increasingly attention. Structures based on the arrayed waveguide grating (AWG) and on-off switches have been reported. DTOF based on AWG may require precision thermal control for AWG usually suffers the problem of temperature dependence. In this talk, we present a novel approach to realize the DTOF (digitally tunable optical filter) based on DWDM thin film filters (TTF) and semiconductor optical amplifier (SOA). Apart from the outstanding feature being consistent with the wavelength comb suggested by international telecommunication union-telecommunication (ITU-T), the proposed DTOF is very stable in temperature performance. Furthermore it requires less SOAs in comparison with the reported structures.

We propose novel large-scale optical-switch architectures that utilize delivery and coupling (DC) switches and wavelength routing (WR) switches based on the cyclic arrayed-waveguide gratings (AWGs). To suppress the passband-frequency deviation inherent in cyclic AWGs, we propose two-stage WR structures in which multiple small-scale cyclic AWGs are cascaded to create a large-scale WR switch. We introduce two configurations for constructing a WR switch; the degrees of the first- and second-stage cyclic AWGs are coprime or not. We fabricate both types of optical switches with planar lightwave circuit technologies. A 270 × 270 switch comprised of coprime cyclic AWGs and a 180 × 180 switch comprised of cyclic AWGs whose degrees have a common divisor are compactly fabricated. Transmission experiments confirm their excellent performance.

All-optical packet switching can overcome limitations of electronic switches in terms of power consumption, speed, cost, and footprint. Switch architectures combining wavelength converters and fiber delay lines provide tunable routing and contention resolution when used with an N×N arrayed waveguide grating (AWG), a key passive optical component to bypass electronic processing limitations. An AWG passively routes either single or multiple input port wavelengths to output ports. A single wavelength per port strategy reduces crosstalk within the AWG, but drastically increases the dimensionality of the device. AWG design constraints due to bandwidth limitations and fabrication processes limit the port number for the foreseeable future to under 100. In order to scale optical switches to emerging network requirements, we must use multiple wavelengths per port. In this paper, we examine several optical router architectures for data center applications using multiple wavelengths per port, and quantify the physical layer impairments. We consider not only the AWG crosstalk, but also Q-factor degradation caused by the multiple wavelength conversions occurring when a packet is buffered for contention resolution. We present the results as a function of the number of recirculations for on–off-keying (OOK) signal formats. While previous work has addressed this issue in terms of accumulated loss, we focus on accumulated intensity noise due to crosstalk and amplified spontaneous emission (ASE). We compare the routing performance of each architecture, and we point out that the AWG crosstalk and accumulated ASE noise during packet recirculation are both critical to the routing performance.

We report an SOI based 1×4 coarse wavelength-division-multiplexer (CWDM) planar concave grating multiplexer/demultiplexer and its application in re-configurable optical add/drop multiplexer (ROADM) system. We employed recursion numerical method to build a low aberration, non-circle grating circle model of concave grating. We fabricated the device using CMOS compatible silicon planar integration technology. The concave grating multiplexer wavelengths are well fitted within ITU-T standard. We also fabricate a prototype of ROADM comprising two CWDMs and four wide-band optical switches. The ROADM function performance is presented.

Arrayed Waveguide Grating (AWG) functioning as a demultiplexer is designed on SOI platform with rib waveguide structure to be utilized in coarse wavelength division multiplexing-passive optical network (CWDM-PON) systems. Two design approaches; conventional and tapered configuration of AWG was developed with channel spacing of 20 nm that covers the standard transmission spectrum of CWDM ranging from 1311 nm to 1611 nm. The performance of insertion loss for tapered configuration offered the lowest insertion loss of 0.77 dB but the adjacent crosstalk gave non-significant relation for both designs. With average channel spacing of 20.4 nm, the nominal central wavelength of this design is close to the standard CWDM wavelength grid over 484 nm free spectrum range (FSR).

Summary form only given. Advances in arrayed waveguide gratings (AWGs) allow monolithic integration of a wide variety of devices using guided-wave photonics. One particular application of interest is beam steering. Beam steering devices implemented in a guided-wave architecture are attractive in optical signal processing, packet switching and laser displays. Various means of achieving efficient beam steering have been explored to date. Our approach is based on using quantum well intermixing technology to integrate a tunable DBR laser with an AWG device.

We present a compact 4x8 wavelength-routing switch that monolithically integrates fast tunable wavelength converters (TWCs) and an arrayed-waveguide grating (AWG) for optical packet switching. The TWC consists of a double-ring-resonator-coupled tunable laser which allows rapid and stable switching, and an optical gate based on a parallel amplifier structure which prevents an input optical signal from being routed through the AWG (filter-free operation). A deep-ridge waveguide technology, employed for the AWG and ring resonators, facilitates the fabrication of the switch and makes the device compact. The filter-free TWCs achieve low crosstalk of the input optical signal of less than -22 dB. The wavelength routing operation of a non-return-to-zero (NRZ) signal at 10 Gbit/s is achieved with a switching time of less than 5 ns.