Photonic Bandpass Filter Research Articles

Microwave photonic bandpass filter using a multiwavelength semiconductor-optical-amplifier ring laser

This paper presents the proposal and experimental demonstration of a microwave photonic bandpass filter structure based on a multiwavelength semiconductor optical amplifier (SOA) ring laser, an optical phase modulator, and a segment of single-mode fiber as a dispersive element. Experimental results show multiple-tap microwave photonic bandpass filter by using a power-equalized multiwavelength SOA ring laser as the optical source. Two laser configurations, one with a linearly chirped fiber Bragg grating (LCFBG) to compensate the dispersion of the laser cavity and one without the LCFBG, are compared for their multiwavelength laser outputs and the corresponding microwave photonic bandpass filters' response. The two microwave photonic bandpass filters have free spectral ranges (FSRs) ~1.26 GHz and 1.85 GHz. The maximal main-to-secondary sidelobe ratio of the microwave filter is above 10 dB.

전기적으로 가변되는 전달특성을 갖는 폴리머 링 광공진기를 이용한 마이크로웨이브 대역통과 필터

An integrated photonic K-band microwave bandpass filter has been proposed and demonstrated by incorporating a polymeric ring resonator. Its transfer characteristics were adjusted by shilling the resonance wavelength of the ring resonator via the thermooptic effect. The achieved performance of the filter includes the center frequency of 20 GHz, the attenuation of , the bandwidth of 2 GHz, and the corresponding quality factor of 10. The microwave output power within the passband of the device was adjusted at the rate of about 6.7 dB/mW in the range of 27 dB. This kind of device with electrically controllable transfer characteristics can be applied to implement microwave switches and other devices.

Tunable photonic microwave bandpass filter using phase Modulation and a chirped fiber grating in a Sagnac loop

We propose a novel all-optical microwave bandpass filter configuration, which uses phase modulation and a linearly chirped fiber grating in a Sagnac loop. The free spectral range (FSR) of the filter can be tuned continuously by tuning the grating. We also derive an expression for the filter transfer function. Calculated and measured results, which agree well, are presented to show a large notch rejection and an easily tunable FSR.

Photonic bandpass filter for 1550 nm fabricated by femtosecond direct laser ablation

A bandpass filter, based on the one-dimensional photonic band-gap crystal concept, was fabricated using an ultrafast laser. As predicted by theory, a high-transmission window appeared in the band gap. The photonic crystal operates in the 1550 nm region. A high machining accuracy of ∼15 nm was achieved during our investigation, which is the key for the operability of the photonic device.

Photonic bandpass filters with high skirt selectivity and stopband attenuation

A new photonic signal processor topology that simultaneously achieves both a high-Q and a high skirt selectivity and stopband attenuation filter response is presented. It is based on a novel dual-cavity bandpass optical structure in which two pairs of active fiber Bragg grating cavities are used with an optical gain offset to control the poles and stopband attenuation characteristics of the filter. This concept enables a large improvement in the filter stopband attenuation, rejection bandwidth, and skirt selectivity to be realized. Measured results demonstrate both a narrow bandpass bandwidth of 0.4% of center frequency and a skirt selectivity factor of 16.6 for 40 dB rejection, which corresponds to a 6.5-fold improvement in comparison to conventional single cavity high-Q structures. To our knowledge, this is the best skirt selectivity reported for a photonic bandpass filter to date. The new photonic filter structure has been experimentally verified and excellent agreement between measured and predicted responses is shown.

Photonics-based interference mitigation filters

New photonic filter structures for interference mitigation of microwave signals are presented. These fiber filters have a parallel topology, and comprise a grating based photonic bandpass filter, or a dual offset cavity structure based on a new noncommensurate delay-line approach. The new topologies overcome the problem of synthesizing both a narrow stopband and a very-wide and flat passband, to simultaneously excise interference with minimal impact on the wanted signal over a wide microwave range. Results demonstrate stopbands of around 1% of center frequency, wide-band flat transmission, and a shape factor of 10.5 that is the lowest reported for a photonic notch filter, in excellent agreement with predictions.