Frequency Selection Switch Research Articles

RF Frequency Selective Switch by Multiple PMIM Conversions

Nowadays, broadband and multi-channel radio frequency (RF) processing has been widely used in communication, radar, countermeasure, and other applications. At present, multiple-input and multiple-output (MIMO)-oriented microwave photonic signal processing technology is relatively scarce, so this paper proposes an RF frequency selective switch (FSS) based on multiple phase modulation to intensity modulation (PMIM) conversions. PMIM conversion has been used in narrowband microwave photonic filtering in the past. We extend it to a wideband and arbitrarily reconfigurable RF spectrum processing unit through an optical frequency comb and periodic optical filter. Although we use the incoherent combination of a multi-wavelength light source, we can obtain any frequency response including rectangles only by using all positive tap coefficients. Using an optical wavelength selective switch (WSS), we obtain RF FSS, and the spectral resolution of RF FSS is much better than that of optical WSS, which is improved by more than two orders of magnitude. The above principles, including single-channel reconfigurable filtering and multi-channel RF FSS, are verified by experiments. Our technology provides a stable solution for future RF MIMO signal processing.

Low power third harmonic generation and all-optical switching by graphene surface plasmons

In this study, we aimed at optimizing the nonlinear properties of the guiding structure of graphene surface plasmon polaritons. The structure is a graphene–metal hybrid waveguide with applicable mode confinement. Focusing electromagnetic power in the graphene sheet improves the harmonic conversion efficiency (0.2% (−27 dB)) and high self-phase modulation. The third harmonic generation phase-matching condition was satisfied in three-dimensional simulations for longer harmonic generation length. Low loss performance is vital for devices that operate in the terahertz regime (0.3–30 THz), because of the low efficiency offered by the available terahertz pulse generation methods. In this study, low loss propagation was achieved by engineering the chemical potential of graphene. Finally, a frequency-selective all-optical switch was designed by placing a subwavelength resonator in the waveguide. Self-phase modulation enabled optical control of the frequency-selective switch.

Design of switches and beam splitters by use of chaotic cavities

We propose the construction of electromagnetic (or electronic) switches and beam splitters by use of chaotic two-dimensional multiport waveguides. A prototype two-port waveguide is locally deformed to produce a ternary incomplete horseshoe characteristic of mixed phase space (chaotic regions surrounding islands of stability where motion is regular). Owing to tunneling to the phase-space stability islands, quasi-bound states (QBS) appear. Then we attach transversal ports to the waveguide in the deformation region in positions where the phase-space structure is only slightly perturbed. We show how QBS can be guided out of the waveguide through the attached transversal ports,giving rise to frequency-selective switches and beam splitters.

Efficient routing and wavelength assignment for reconfigurable WDM networks

Through the use of configurable wavelength-division-multiplexing (WDM) technology including tunable optical transceivers and frequency selective switches, next-generation WDM networks will allow multiple virtual topologies to be dynamically established on a given physical topology. For N node P port networks, we determine the number of wavelengths required to support all possible virtual topologies (PN lightpaths) on a bidirectional ring physical topology. We show that if shortest path routing is used, approximately N wavelengths are needed to map N lightpaths. We then present novel adaptive lightpath routing and wavelength assignment strategies that reduce the wavelength requirements to [(N/2)] working wavelengths per port for protected networks and [(N/3)] wavelengths in each direction per port for unprotected networks. We show that this reduced wavelength requirement is optimal in the sense that it is the minimum required to support the worst case logical topology. Furthermore, we prove that a significant number of logical topologies require this minimum number of wavelengths. We also develop joint routing and wavelength assignment strategies that not only minimize the number of wavelengths required to implement the worst case logical topologies but also reduce average wavelength requirements. Finally, methods for extending these routing and wavelength assignment results to general two-connected and three-connected physical topologies are presented.

Multichannel frequency-selective switch employing an arrayed-waveguide grating multiplexer with fold-back optical paths

The optimized configuration of an N-channel frequency-selective 2/spl times/2 switch based on an arrayed-waveguide grating (AWG) (2N+1)/spl times/(2N+1) multiplexer is proposed that offers significant crosstalk reduction and loss-imbalance equalization. The optimization is achieved by employing fold-back optical paths instead of loop-back paths. A switch constructed with a silica-based AWG 16/spl times/16 multiplexer demonstrates coherent crosstalk of less than -30 dB in the transmitting frequency-division-multiplexed (FDM) channels; the gain in optimization is more than 15 dB. The largest loss-difference among the seven FDM channels is simultaneously reduced from 4.5 dB to 1.6 dB. These improvements will extend the cascadable number of nodes in all-optical FDM networks. >

Frequency stability of a waveguide-type frequency selection switch for optical FDM distribution systems

This work describes the frequency stability of a 128-channel waveguide-type frequency selection switch (FSSW) for optical FDM distribution systems. Special attention is given to crosstalk level degradation due to chip temperature changes. First, the allowable total crosstalk level for the FSK-direct detection scheme is discussed both theoretically and experimentally. Next, taking the crosstalk degradation into consideration, the allowable ambient temperature change is estimated. Finally, the influence of the applied power change in the switching operation is evaluated. As a result, it is estimated that the FSSW is sufficiently stable without additional feedback loops, even if the ambient temperature change is wider than +or-43 degrees C.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

128-channel polarization-insensitive frequency-selection-switch using high-silica waveguides on Si

A 128-channel polarization-insensitive frequency-selection-switch (FS-SW) with 10-GHz frequency spacing is discussed. The FS-SW was fabricated on Si using low-loss GeO/sub 2/-doped high-silica waveguides, and its frequency-insensitive operation was attained by the laser trimming adjustment of a-Si film which controls waveguide birefringence. The fiber-to-fiber loss of the transmitted channel was 6.7 dB in the pigtailed FS-SW and the total crosstalk level was less than -13 dB. By using this FS-SW, a 100-channel optical frequency division multiplexing (FDM) transmission-distribution experiment at 622 M b/s over a 50-km fiber length was achieved.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

100-channel optical FDM transmission/distribution at 622 Mbit/s over 50 km utilising a waveguide frequency selection switch

100-channel optical FDM transmission/distribution at 622 Mbit/s is demonstrated for a fibre length of 50 km. A polarisation-insesitive waveguide frequency-selection-switch with 10 GHz intervals and an FSK/direct-detection scheme using a Mach–Zehnder filter type optical frequency discriminator are verified as feasible.

A 16-channel frequency selection switch for optical FDM distribution systems

The performance of a 5-GHz-spaced, 16-channel frequency selection switch (FS-SW) for optical frequency division multiplexing (FDM) distribution systems is described. The silica waveguide-type FS-SW is constructed with four serially connected periodic filters integrated on a silicon chip. The required crosstalk level for each periodic filter of the FS-SW was estimated to be -21.0 dB for a 16-channel FS-SW and 23.6 dB for a 128-channel FS-SW. Crosstalk can be independent of the power coupling ratio of the 3-dB-coupler regions by choosing suitable connecting configurations for the periodic filters. A controller for the switch is also described and the desired channel can be selected successfully from among 16 optical carriers under an average crosstalk level of less than -20 dB. >

A 100-channel optical FDM transmission/distribution at 622 Mb/s over 50 km

A 100-channel optical frequency-division multiplexing (FDM) transmission/distribution experiment at 622 Mb/s is demonstrated for a fiber length of 50 km. The feasibility of a polarization-insensitive waveguide frequency selection switch for 10-GHz intervals and a frequency-shift-keying (FSK) direct-detection scheme employing a Mach-Zehnder filter is verified. The demodulation circuit employs a Mach-Zehnder filter and a balanced receiver, which utilizes optical power more efficiently than the Fabry-Perot filter. No receiver sensitivity degradation is observed due to interchannel crosstalk of the 128-channel tunable waveguide frequency selection switch (FS-SW) or fiber four-wave mixing for transmissions over a 50-km-long nondispersion-shifted (NDS) fiber and a 26-km-long dispersion-shifted (DS) fiber.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Silica-based integrated optic Mach-Zehnder multi/demultiplexer family with channel spacing of 0.01-250 nm

A Mach-Zehnder (MZ) interferometer design is presented for application to wavelength-division multiplexed/frequency division multiplexed (WDM/FDM) systems. A variety of integrated-optic devices with low loss and low crosstalk, using silica-based waveguides, are demonstrated. MZ interferometers operate as multi/demultiplexers or frequency-selection switches. The channel spacing is determined by the waveguide arm length difference, and a spacing range of 1 GHz to 36 THz, corresponding to a wavelength spacing of 0.008-250 nm, is achieved. The devices for the WDM region have low fiber-to-fiber loss of 0.5 dB, and the devices for the FDM region have higher losses of 2-5 dB. Crosstalk of less than -15 dB was obtained for all the devices. A 5-GHz-spaced 16-channel frequency selection switch and a 10-GHz-spaced eight-channel multi/demultiplexer were also fabricated with a total loss of 5 dB and total crosstalk of -10 dB or less. >

Factors affecting the design of optical FDM information distribution systems

Major factors affecting optical frequency division multiplexing (FDM) distribution system design are described. In particular, multiplexing/distribution configuration and channel-selection methods are compared from the viewpoint of the number of channels, the number of subscribers, and the transmission distance. The applicability of optical fiber amplifiers to the optical FDM information-distribution network is also discussed. The experimental results of a 5 GHz spaced 16-channel FDM distribution/transmission at 622 Mb/s, using a waveguide frequency-selection switch (tunable filter) and a multicarrier frequency-stabilization technique, are also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

16-channel optical FDM distribution/transmission experiment utilising Er 3+ -doped fibre amplifier

A 16-channel optical FDM distribution/transmission experiment at around 1534nm wavelength is demonstrated utilising an Er3+-loped fibre amplifier. 16 intensity-modulated optical signals at 622 Mbit/s were amplified simultaneously at a gain of 15.2–18.5 dB. One of the amplified signals is selected using the waveguide frequency selection switch and directly detected with a receiver sensitivity of −38 dBm (Pa=10−9).

Channel selection and stabilization technique for a waveguide-type 16-channel frequency selection switch for optical FDM distribution systems

A channel selection and stabilization technique for a waveguide-type 16-channel frequency selection switch (FS-SW) was examined at the 1.5- mu m wavelength region. The desired channel could be selected from 16 optical channels with a 5-GHz channel separation. The frequency fluctuation width for the observed short period was 65-250 MHz, and the frequency drift during 30 min was 20-100 MHz. An average crosstalk level of less than -20 dB was successfully achieved in the on state of the FS-SW stabilization.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

16-channel optical FDM distribution/transmission experiment utilising multichannel frequency stabiliser and waveguide frequency selection switch

A 16-channel, 622 Mbit/s optical FDM distribution/transmission system experiment is demonstrated for a fibre length of 13 km. The feasibility of a multicarrier frequency stabiliser and waveguide frequency selection switch for 5 GHz frequency intervals is verified.

A Conceptional Design on Optical Frequency-Division-Multiplexing Distribution Systems with Optical Tunable Filters

Optical frequency-division-multiplexing distribution systems providing more than ten frequency multiplexed optical signals separated by on the order of gigahertz, distribute signals to plural receivers, where one of the signals is selected by a frequency selection switch (FS-SW). This paper describes the design of an optical frequency-divisionmultiplexing distribution system. Investigation is made of periodic filters for frequency division multiplexers and FS-SW, and the optical source, as well as single-mode fiber polarization mode dispersion. Preliminary transmission experiments using a bit rate of 450 Mbits/s, fiber length of 13 km, and frequency spacing of 11 GHz are also demonstrated at a 1.5 μm wavelength to show the design's suitability.