Modulation instability of wave packets in a Gires–Tournois interferometer

We study the specific features of the perturbation dynamics of a wave packet in a Gires–Tournois interferometer. We obtain a dispersion relationship that relates the perturbation parameters to the parameters of the structure and pump wave, the analytical expressions for the gain increment of a harmonic perturbation and other important characteristics that determine the dynamics of the modulation instability of the reflected wave. Based on numerical simulation, we plot the dependences of the dispersion and nonlinearity parameters and the gain increment on the spacing between the interferometer mirrors, the angle of incidence of the radiation onto the mirrors, and the radiation intensity.     

Transmission characteristics of Mach–Zehnder interferometer comb filter based on thermal operation

We propose and experimentally demonstrate switchable and tunable transmission characteristics of a Mach–Zehnder interferometer comb filter based on thermal operation. Its temperature characteristics are investigated to reveal a shift in the peak wavelength position from 0.003 to 0.004 nm/°C and a tunable range of wavelength spacing of 0.76–0.90 nm for maximum and minimum effective lengths, respectively. This configuration provides the unique advantages of an all-fiber structure, tunable wavelength spacing, switchable spectral peaks, independent tuning of the center wavelength and wavelength spacing of the spectral peaks, and low polarization sensitivity. It is relatively simple to fabricate and expected to have applications in temperature fiber optic sensors and multiwavelength fiber laser sources.     

A high performance tunable optical filter based on cascaded polarization interference filter

A new kind of tunable optical filter is proposed for DWDM optical communication application. It is based on cascaded polarization interference filter (PIF). The period and bandpass width of each PIF are decided by its optical path difference between o-ray and e-ray (OPDOE). When their OPDOEs are proportionately designed, the tuning range and bandpass width depend on OPDOE in the first and the last PIF, respectively. The tuning range, bandpass width and crosstalk are independent each other. The crosstalk is related to the OPDOE ratios among PIFs and can be suppressed by designing the PIF's OPDOE. A set of OPDOE is suggested that are l1, 2 × l1, 22 ×l1, 23 ×l1, 24 ×l1, ..., 2N-4 × l1, 15 × 2N-7 ×l1, 10 × 2N-6 × l1 and 2N-2 ×l1 from the first to the last. This suggested OPDOEs can yield -50-dB crosstalk for any tuning range and bandpass width. The insert loss is less than 1 dB. As its loose alignment requirement, there is no limitation on cascaded PIF number. When 11 PIFs are cascaded, it can ach     

Dynamic Mach–Zehnder interferometer based on a Michelson configuration and a cube beam splitter system

We developed simultaneous phase-shifting system based on a Mach–Zehnder interferometer and a replicating system integrated by a Michelson configuration and a cube beam splitter. The system is capable to obtain four simultaneous interferograms in a single capture, and the phase shifts are controlled by placing a linear polarizer in each replica obtained. The system retrieves four interferograms with a relative phase shift of π/2 and the optical phase map is calculated using the four-step algorithm. In addition, the configuration presents potential capabilities for generating spiral interference patterns. To show the advantage of the technique, experimental results are presented for static and dynamic samples.

     

Large-range liquid level sensor based on an optical fibre extrinsic Fabry–Perot interferometer

We propose an efficient approach to develop large-range liquid level sensors based on an extrinsic Fabry–Perot optical fibre interferometer with an all fused-silica structure and CO₂ laser heating fusion bonding technology. The sensor exhibits signatures of a high sensitivity of 5.3 nm/kPa (36.6 nm/psi), a resolution of 6.8 Pa (9.9×10⁻⁴ psi) and an extreme low temperature dependence of 0.013 nm/°C. As a result, a high resolution of the water level measurement of approximately 0.7 mm on the length scale of 5 m and small errors of the water pressure measurement induced by the temperature dependence within 0.0025 kPa/°C (0.00036 psi/°C, water level 0.25 mm/°C) are achieved, thus providing useful applications for the detection of the large-range liquid level in harsh environments.     

Ultrafast all-optical demultiplexer based on monolithic Mach–Zehnder interferometer with integrated semiconductor optical amplifiers

A monolithically integrated and fully packaged Mach–Zehnder interferometer with semiconductor optical amplifiers (MZI-SOA) is demonstrated as polarisation-independent high-speed demultiplexer for up to 160 Gbit/s optical time division multiplexed (OTDM) data streams.     

Temperature-independent refractometer based on fiber-optic Fabry–Perot interferometer

A miniature fiber-optic refractometer based on Fabry–Perot interferometer (FPI) has been proposed and experimentally demonstrated. The sensing head consists of a short section of photonics crystal fiber (PCF) spliced to a single mode fiber (SMF), in which the end-face of the PCF is etched to remove holey structure with hydrofluoric (HF) acid. A Fabry–Perot interference spectrum is achieved based on the reflections from the fusion splicing interface and the end-face of the core of PCF. The interference fringe is sensitive to the external refractive index (RI) with an intensity-referenced sensitivity of 358.27 dB/RIU ranging from 1.33 to 1.38. The sensor has also been implemented for the concentration measurement of λ-phage DNA solution. In addition, the dip intensity is insensitive to the ambient temperature variation, making it a good candidate for temperature-independent bio-sensing area.     

WDM and DWDM optical filter based on 2D photonic crystal Thue–Morse structure

This paper describes elaboration of two dimensional photonic crystal structures based on Thue–Morse sequence. Our results establish that the optical properties of these aperiodic multilayer systems can be tailored by adjusting either the radius of some cells of the proposed structure or defect characteristics. We introduce a resonant cavity in the proposed structure to select desirable wavelengths for filtering. Bandwidth of selected wavelengths are about 1 nm and suitable for communication applications. Also, our simulations show that efficiency of the proposed structure is enough. The total footprint of proposed filter is 331.24 μm², therefore it is suitable to be integrated in all optical chips.     

Quartz optical filter for wavelength selection of frequency-doubled laser based on optical rotatory dispersion effect

Based on the optical rotatory dispersion effect,an optical filter for selecting the second harmonic of a frequency-doubled laser is constructed from quartz in combination with polarizers.The operating principle is analyzed by matrix formulation,and the result indicates that the second harmonic of a frequency-doubled laser will be obtained when the rotation angle has a difference of(2n 1)π/2 (n=0,1,2,3,...)between the two polarizations of the second-harmonic laser and the fundamental laser.The spectrum of the output laser is taken by the AQ-6315A spectrometer,and the experimental results are in good agreement with the theoretical results.     

A novel subwavelength plasmon-polariton optical filter based on tilted coupled structures

This work proposes a completely new approach for the design of resonant structures aiming at wavelength-filtering applications. The structure consists of a subwavelength metal-insulator-metal (MIM) waveguide presenting tilted coupled structures transversely arranged in the midpoint between the input and output ports. The cavity-like response of this device has shown that this concept can be particularly attractive for optical filter design for telecom applications. The extra degree of freedom provided by the tilting of the cavity has proved to be not only very effective on improving the quality factor of these structures, but also to be an elegant way of extending the range of applications for tuning multiple wavelengths, if necessary.     

Design of three-primary-color filter based on structure of three-cavity Fabry–Perot color filter

Optical and Quantum Electronics - Elastic optical network (EON) is considered as the platform for future optical transport networks. Routing and spectrum allocation (RSA) has a significant bearing...     

Signal amplification based on the local nonlinear Mach–Zehnder interferometer

Using the phase modulation of spatial solitons, a new scheme for all-optical signal amplification has been proposed in this paper. The considered structure is composed of the nonlinear Mach–Zehnder interferometer (NMZI) with the straight control waveguide (CWG), the uniform nonlinear medium (NLM) and the linear output waveguide. The local NMZI functions like a phase shifter. The light-induced index changes in the local nonlinear MZI are responsible for the input beam routing in the uniform nonlinear medium. The coupling of the input beam to the output waveguide depends on its propagation direction in the NLM. It is shown that the signal launched at CWG can deflect the beam launched at the NMZI (input beam) and a modulated (amplified) output could be obtained at the output waveguide. Further, signal pulse may be reshaped by appropriately increasing the NLM length. In addition, amplification factor may be enhanced by increasing the NLM length and injecting an appropriate continuous wave beam along with the signal beam at CWG.     

Micro-Mach–Zehnder interferometer based on MMI used in seismic accelerometer

This paper describes a micro-Mach–Zehnder (M–Z) interferometer used in seismic accelerometer. To achieve high modulation efficiency and a small chip size, a deeply etched ridge waveguide structure is employed, and accordingly a multi-mode interference (MMI) coupler is used as the 1 × 4 power splitter. The result of Beam Propagation Method (BPM) simulation indicates that the phase shift is linearly corresponding to the applied acceleration.     

Analysis of twisted nematic liquid crystal Fabry–Perot interferometer (TN-FPI) filter based on the coupled mode theory

The tuning characteristics of a twisted nematic (TN) liquid crystal (LC) Fabry–Perot interferometer (FPI) wavelength filter, which is a basic component of wavelength division multiplexed transmission systems, is analyzed using coupled mode theory. First, a simplified modeling of the refractive index change in the LC layer is presented. Next, various characteristics of the eigen polarization modes of the LC medium and the cavity are derived analytically. Finally, the qualitative interpretation of the behavior of the FPI's resonance spectrum are given.     

Temperature-insensitive refractive index sensor based on an optical fiber extrinsic Fabry–Perot interferometer processed by a femtosecond laser

An optical fiber extrinsic Fabry–Perot interferometer(EFPI) is designed and fabricated for refractive index(RI)sensing.To test the RI of liquid,the following two different methods are adopted:the wavelength tracking method and the Fourier-transform white-light interferometry(FTWLI).The sensitivities of sensors with cavity lengths of 288.1 and 358.5 μm are 702.312 nm/RIU and 396.362 μm/RIU,respectively,by the two methods.Our work provides a new kind of RI sensor with the advantages of high sensitivity,mechanical robustness,and low cross sensitivity to temperature.Also,we provide a new method to deal with gold film with a femtosecond laser.     

Stable multi-wavelength thulium-doped fiber laser based on all-fiber Mach–Zehnder interferometer

We propose and experimentally demonstrate a multi-wavelength thulium-doped fiber（TDF） laser based on all-fiber Mach–Zehnder interferometer（MZI） at 1.9 mm. Here a segment of 4 m single-mode TDF is pumped by 1568 nm fiber laser for 2 mm band optical gain. The MZI includes two cascaded 3 d B coupler. A segment of 3.5 m long un-pumped polarization-maintaining TDF and polarization controller（PC） are joined in the ring cavity to suppress the mode competition. Multi-wavelength lasers at 1.9 mm with wavelength number from one to four are obtained by adjusting the PC and the stability of output power of multi-wavelength fiber laser is analyzed.     

Solar-blind ultraviolet band-pass filter based on metal–dielectric multilayer structures

Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.     

A novel time-to-live countdown scheme based on asymmetric Mach-Zehnder interferometer and Fabry-Perot semiconductor optical amplifier

We propose a novel optical time-to-live (TTL) processing scheme using asymmetric Mech-Zehnder interferometer (AMZI) and Fabry-Perot semiconductor optical amplifier (FP-SOA). AMZI transfers M TTL pulses into M-1 pulses and two residual pulses with 6-dB power difference. FP-SOA enhances the power difference between the M-1 pulses to the residual pulses to more than 10 dB. A numerical model is established for verifying the feasibility of this scheme.     

Refractometer based on a tapered Mach–Zehnder interferometer with Peanut-Shape structure

A novel refractometer based on tapered Mach–Zehnder modal interferometer (MZI) is proposed and experimentally demonstrated. This sensor is composed of a pair of Peanut-Shape structures and an embedded taper – the former excites high-order cladding modes, while the latter enhances the evanescent field. As the effective refractive index (RI) of cladding is based on the changes of surrounding RI, thus extinction ratio will change due to the alteration of the distribution of power in the fiber which is induced by various differences of core and cladding for RI. As a result, the maximum RI sensitivity of 240.78 extinction ratio/RIU (refractive index unit) is achieved within the range from 1.3334 to 1.4081.