Fiber-optic Phase Modulator Research Articles

A Graphene-Enhanced Fiber-Optic Phase Modulator With Large Linear Dynamic Range

We propose a graphene-based modulator integrated into currently used communication fibers. The graphene is directly built into the core of the fiber to ensure the coupling efficiency. The fiber is deliberately side-polished to enhance the light-graphene interaction. The two-dimensional model analysis method and three-dimensional finite difference time domain method are used to rigorously disclose the light modulation mechanism under the anisotropic graphene modeling, which is merely conducted in previous studies. Based on such a structure, a phase modulator with an arm length of 127 μm is numerically demonstrated with enhanced modulation efficiency. A quasi-linear relation between the phase change and chemical potential of graphene is found theoretically for the first time, providing a large linear dynamic range to control the phase of optical modulation.

Experimental study on coherent beam combination of fiber amplifiers using adaptive power-in-the-bucket cost function

Beam combination (BC) of fiber amplifiers based on master-oscillator-power-amplifier configuration is an outstanding way to generate high power and high beam quality laser output, where the tip/tilt aberrations among beamlets are considered as a serious influence factor to BC effects. In this paper, a new tip/tilt control method based on adaptive power-in-the-bucket (PIB) cost function is proposed to solve the problem of restricted tip/tilt correcting value in current BC systems. Experimental setup of coherent BC of two-channel 2 W fiber amplifier array is established. Home-made piezoelectric-ring fiber-optic phase-modulator and adaptive fiber-optics collimator are employed to correct piston-and tip/tilt-type aberrations, respectively. The feasibility of proposed tip/tilt control method using adaptive-PIB is demonstrated and nice effect of coherent BC is achieved.

A fiber optic phase modulator with an optical frequency shift of up to 20 GHz

A fiber optic phase modulator is described in which the phase of a light wave traveling in an optical fiber is modulated by a composite electromechanical resonator with Q≌1000. The instantaneous frequency of the wave at the modulator output varies according to a harmonic law. The interval of tuning of the instantaneous light wave frequency achieved in the experiment is 20 GHz, which corresponds to a modulation index of ≌106. It is demonstrated that a maximum value of the frequency tuning range is determined by the elastic limit of the resonator material.

Piezoelectric fiber optic phase modulator with a reduced level of spurious polarization modulation

It is experimentally demonstrated that a tenfold decrease in the level of spurious polarization modulation can be achieved in a fiber optic phase modulator comprising two fiber sections featuring the polarization mode conversion, arranged on the same piezoelement.

Performance of Optical Fiber Based Phase Modulators and the Effects of Ambient Temperature

The optical fiber phase modulator is an important component in fiber opiie interferometers f sensors, where the modulation is achieved by physically varying the parameters such as the refractive index or the length of the optical fiber. The fiber optic phase modulator is normally realised by wrapping a fiber on piezo-electric transducer (PZT), usually of cylindrical form. It is difficult to rely purely on published data of piezoelectric constants, because the performance depends critically on the dimensions of the cylinder and the type and compositions of the PZT material. Hence, it is essential that the phase modulator is calibrated before being put to an application. The paper contains description of existing theories of phase modulation, comparison of experimental results with theoretical predictions, and phase dependance on ambient temperature

Fabrication and structural analysis of ZnO coated fiber optic phase modulators

Fiber optic modulators were fabricated by coating optical fibers with electrode and piezoelectric ZnO layers. The techniques of piezoelectric fiber optic modulator (PFOM) fabrication are presented, and the microstructure and crystallographic texture of the coatings are analyzed. In order to produce thick (approximately 5 μm) ZnO coatings, it was necessary to study the reactive dc magnetron sputtering process in O2/Ar gas mixtures under conditions close to the transition between an oxidized and nonoxidized Zn target surface. In situ quartz crystal microbalance measurements of the deposition rate revealed thee distinct regions in the deposition rate (R) vs oxygen partial pressure behavior, at constant total pressure, for sputtering under conditions that provided an oxidized Zn target surface. Additionally, a transition between oxygen and argon dominated sputtering as observed by varying the sputtering pressure while maintaining a constant The transition between oxygen and argon dominated sputtering influences R to varying extents within the three R vs regions for an oxidized target surface. Correlations among the cathode current and voltage, deposition rate, and gas flow rate are presented to give a better understanding of the reactive sputtering processes occurring at the oxidized Zn target surface. Sputtering conditions optimized for a high ZnO deposition rate were used to produce 〈001〉 radially oriented ZnO fiber coatings for PFOM devices that can produce optical phase shifts as large as 0.38 rad/V.

Technique for stabilizing the phase of the reference signals in analog fiber-optic links

The effects of temperature and longitudinal stress on the phase delay of reference signals in a fiber-optic link are discussed. A feedback system that uses a fiber-optic phase modulator is used to compensate for the phase fluctuations of a reference signal in the link. The phase deviations of a 50-MHz reference frequency that are caused by temperature variations of the link is reduced by more than 95% on optimization of the correction system. The advantages of this technique are that the fiber-optic phase modulator has a greater stability compared with the electronic phase modulators, and signal conversions from electric to optic and optic to electric are avoided.

Birefringence modulation in fiber-optic phase modulators

We report an unusually large birefringence modulation in fiber-optic phase modulators formed with cylindrical piezoelectric transducers when driven at a few hundred kilohertz. The magnitude of the birefringence modulation is a strong function of modulation frequency. A simple model is used to explain the phenomenon, and the theoretical predictions agree well with the experimental results.

Frequency response and phase-shift nonlinearity of a cylindrical PVF/sub 2/-film-based fiber-optic phase modulator

A cylindrical coil configuration for a polyvinylidene-fluoride (PVF/sub 2/)-film-based fiber-optic phase modulator is studied, focusing on the frequency response and the nonlinearity of the phase shift at the resonant frequency. This configuration, hitherto used for PVF/sub 2/ film modulators, offers resonance at well-defined, controllable, and higher frequencies than possible for the flat-strip configuration. Two versions of this configuration that achieve selective mode suppression or enhancement and hence provide a choice of the resonance frequency at which a large phase shift occurs are presented. It is shown that a coil version in which the fiber loops are bonded strongly to each other leads to large reduction in the phase shift. A comparative study of the existing piezoelectric fiber-optic phase modulator designs is also presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Wide-frequency fiber-optic phase modulator using piezoelectric polymer coating

The highly sensitive response of a fiber-optic phase modulator that is coated with 80-90- mu m-thick vinylidene fluoride/trifluoroethylene copolymer on an 80- mu m-diameter single-mode fiber and made piezoactive by radial poling is demonstrated over a wide frequency range, from 500 Hz to 50 MHz. In the range of 10 kHz up to 2 MHz, a relatively flat response is measured, whereas at high frequencies between 6 and 50 MHz, the phase modulation exhibits multiple peaks dominated by radial resonances of the fiber-jacket composite. Theoretical considerations on the phase shift and experimental results are given. >

Integrated fiber optic phase modulators

Fiber optic phase modulators have been fabricated by coating single-mode fibers with piezoelectric copolymers of PVF 2-TFE. The phase sensitivity of such a fiber has been studied both analytically and experimentally over a wide frequency range (1 kHz–350 MHz). Such fibers can be utilized as phase modulators or as electric field sensors.