Filter Tuning Range Research Articles

High selectivity and compact tunable bandpass filter using YIG material

This paper presents a novel highly selectivity tunable filter with transmission zero. Yttrium iron garnet/gadolinium gallium garnet layer structures are added to the filter structure as bandstop units to achieve transmission zero. CST Studio Suite simulates and optimizes the filter structural parameters. Transmission zero and filter passband are tuned simultaneously. Skirt selectivity can be significantly increased by placing the transmission zero at the lower side of the filter passband. The parasitic response can be suppressed by about 20 dBc when the transmission zero is located on the upper side of the filter passband. With the magnetic field shifted from 3250 to 5005 Oe, the filter tuning range is 11–16 GHz with an insertion loss of about 3.5 dB. The addition of transmission zero enhances filter selectivity and provides more flexibility in suppressing interfering signals that vary in frequency or parasitic responses at specific frequencies. This method presents an approach for designing wide tuning range filters with transmission zeros.

Applications of the frequency locking effect in acousto-optic systems for control of optical radiation spectral composition

A spectral optoelectronic system combining a collinear acousto-optic (AO) cell and positive electronic feedback is examined. The operation of this system in the generation mode and possibilities of practical application of the locking effect of the system’s self-oscillations for controlling the optical radiation mode composition of semiconductor lasers are studied. The design and test results of the new AO device, which can be treated as a time-domain optical demultiplexer, are described. This demultiplexer also applies the frequency locking effect. The demultiplexer model presented achieves the following characteristics: the wavelength spacing between channels is less than 0.6 nm; the channel passband width is 0.4 nm; the crosstalk attenuation between adjacent channels is more than 42 dB; insertion loss is less than 2 dB; and the optical tuning range of the demultiplexer corresponds to the AO filter tuning range, which is not less than one octave.

The study of an ultrawide tunable range single passband microwave photonic notch filter

A single passband tunable microwave photonic notch filter with ultrawide tunable range is presented. It is based on dual-drive Mach-Zehnder modulator and stimulated Brillouin scattering. By introducing two pump signals whose frequency interval equals twice of the Brillouin frequency shift, the available filter tuning range can reach 4fB. With the increase of the number of pump light the tuning range of the filter will grow proportionally. The amplitude of the output signal of the notch filter changes with the half-wave voltage and a DC bias voltage of DDMZM.

A Half-Mode Substrate-Integrated-Waveguide Tunable Filter Using Packaged RF MEMS Switches

A two-pole, half-mode substrate-integrated-waveguide (HMSIW) RF MEMS tunable filter with 28% tuning range around 1.4 GHz is presented. The filter occupies a total area of λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> × 0.7λg @ 1.4 GHz and exhibits an insertion loss of 1.2-3.4 dB, return loss better than 11 dB and quality factor of 75-140 for all tuning states, while having excellent linearity. The filter maintains a constant absolute 1 dB bandwidth of 85 ±10 MHz over the filter tuning range. Circuit models for the tunable HMSIW resonator and a methodology for systematic filter design are also described in detail.

Wide range electrostatic MEMS Fabry Perot optical tunable filter: modelling an electrostatic and mechanic beam deflection

A novel wide range electrostatic microelectromechanical system floating Fabry Perot optical tunable filter (MEMS f-FPOTF) is modelled and analyzed in terms of its electro-mechanic behaviour. The composite beam approach has been used to model the floating Fabry Perot cavity. The floating dual membrane FPOTF consists of multi layer Si/SiO2/Si thin films with an optical cavity in the middle structure. The filter tuning range has been improved by utilizing bonded silicon on insulator wafers that permits the floating cavity to be deflected both ways; up and down. Electro-mechanic analysis shows a 7% (STRUCTURE1) and 5% (STRUCTURE2) difference between analytical and finite element modelling in which the 7% difference in light incident angle contributes to a 0.5 nm shift while the 5% difference in length of cavity indicates a 4 nm shift in MEMS f-FPOTF operating wavelength. This analysis validates the analytical modelling of this device as a wavelength selector in coarse wavelength division multiplexing.

Coherence-Free Equivalent Negative Tap Microwave Photonic Notch Filter Based on Delayed Self-Wavelength Conversion

A new coherence-free single-wavelength microwave photonic notch filter, which is widely tuneable, and which is compatible to be inserted in a conventional fiber-optic link, is presented. It is based on self-wavelength cross gain modulation in a semiconductor optical amplifier placed at an off-centre location in a Sagnac loop. The structure can realize a high free spectral-range negative tap notch filter response, and does not have any coherent interference and phase-noise limitations. Moreover, it enables widely tunable notch filtering to be simply realized. Experimental results are presented which demonstrate a large continuous filter tuning range of an octave, robust operation with a narrow linewidth source, and wide passband notch filtering operations.

40-nm-wide tunable fiber ring laser with single-mode operation using a highly stretchable FBG

We demonstrate a 750-Hz linewidth single-mode erbium-doped fiber (EDF) ring laser with wide tunability using a widely tunable fiber Bragg grating (FBG). The stable single-mode operation is realized by using the FBG as a narrow wavelength-selective element and 4 m of unpumped EDF as a saturable absorber in the cavity. The 40-nm continuous tuning range of 1522-1562 nm is achieved using a highly stretchable FBG that exhibits a filter tuning range of over 52 nm. The grating is prepared with chemically stripped deuterium-loaded fiber to eliminate degrading factors for the grating strength, thereby achieving the wide tunability. The tuning range represents a 3.5-fold increase in wavelength tuning over previous use of FBGs.

Magnetically tunable millimetre-wave filter with single-crystal barium ferrite

Barium-ferrite (BaFe12O19) single crystals with a high anisotropy field and low millimetre-wave (mm-wave) losses have been grown from high-temperature solutions. The high internal field (17/4π MA/m) considerably reduces the external magnetic field required for spin resonance at mm-wave frequencies. Due to the progress in single-crystal barium-ferrite technology, it is possible to extend the tuning range of filters up to 90 GHz. A compact tunable filter, similar to y.i.g.-filters, has been built and the first results are reported.