Multifunction optical filter with a Michelson-Gires-Tournois interferometer for wavelength-division-multiplexed network system applications

We propose using a novel multifunction optical filter with a Michelson-Gires-Tournois interferometer (MGTI) for future smart wavelength-division-multiplexed network system applications. The MGTI filter is a typical Michelson interferometer in which one of its reflecting mirrors is replaced with a Gires-Tournois resonator. One unique feature of this device is that it can function as a channel-passing (CP), a channel-dropping (CD), or a wide-bandpass (BP) filter, depending on the interferometer arm-length difference. Other interesting features are that (1) the linewidths of both the CP and the CD filter are twice as narrow as that of a typical Fabry-Perot filter with similar parameters, (2) theoretical visibility is always unity regardless of the mirror reflectance value, and (3) the BP filter has an excellent boxlike response function. Numerical results showing these characteristics are presented.     

A Differentiating Fiber-optic Ring Interferometer

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集成马赫-曾德尔热光耦合器的可调谐振环优化设计

根据耦合模理论,推导出可调谐光波导谐振环的光强和相位传递函数的表达式,并分析了可调谐谐振环的传输特性.结果表明,谐振环中集成的马赫-曾德尔耦合器的参量设定和调谐方式直接影响谐振环的谐振频率移动范围和调制功率.通过改变耦合器参量对谐振环进行优化设计,在中心波长为1550 am附近,谐振环半径2 cm,传输损耗0.08 dB/cm的情况下,实现了清晰度和最佳谐振深度的调谐,谐振频率的移动范围低于0.027 GHz,降低了谐振环对频率调制器的调频要求,同时降低了耦合器的调制功率.     

Analysis of a second-order polarization-independent filter made of a single ring resonator and a Sagnac interferometer

A novel second-order polarization-independent filter made of a single ring resonator and a Sagnac interferometer (SRRSI) is proposed, and its filtering characteristics are investigated. By using birefringence in waveguide, a single ring resonator can be used to synthesize a filter with second-order response. Analytical formulas are derived for characteristics of the SRRSI varied with waveguide parameters, such as the coupling coefficient; and the critical condition of a second-order Butterworth filter is given. The influence of loss in the ring resonator is also analyzed.     

Tunable asymmetric fibre ring resonator

A fibre ring resonator with coupling via an asymmetric twin-core single-mode coupler with variable mismatch is analysed. It is found that by varying the mismatch in the coupler the resonance conditions of the ring are also changed. Suitable choices of device parameters allow the resonance to be tuned over a range of wavelenths by altering the coupler mismatch.     

基于对称结构的光纤谐振环辅助马赫曾德尔干涉仪型梳状滤波器的研究

为了改善常规马赫曾德尔干涉仪(MZI)型滤波器的输出特性, 提出了一种由双耦合器和单模光纤构成的“8”字形谐振环,将该光纤谐振环与一个3 dB光纤方向耦合器相结合,利用光纤谐振环反馈回路引入的相位调节效应,选择合适的谐振环耦合角,设计出一种基于对称结构的光纤谐振环梳状滤波器,具有平坦滤波响应的输出光谱。与普通MZI型梳状滤波器和双级级联MZI型梳状滤波器相比,阻带抑制和过渡带滚降特性明显加强;与不对称结构的光纤谐振环辅助MZI型梳状滤波器相比,在考虑传输损耗的情况下,相干涉的两束光信号不存在幅度差异,降低了传输损耗对梳状滤波器消光特性的影响。     

Gravitational wave detection using dual input Michelson interferometer

We propose a new scheme for interferometric gravitational wave detection using a dual input Michelson interferometer. The scheme allows us to put a phase modulator outside the interferometer without requiring arm-length unbalance. Moreover, the scheme can realize sub-shot-noise sensitivity using an amplitude squeezed state of light as one of the dual inputs.     

Demonstration of a recombined Fabry-Perot-Michelson interferometer with suspended mirrors

We describe preliminary experimental results concerning the operation of a 3 m arm-length Michelson interferometer with two Fabry-Perot cavities whose mirrors and beam splitter are suspended independently by wires. The reflected light beams from the two Fabry-Perot cavities are recombined to obtain interference at a photo-detector; this scheme is necessary for future power-recycled laser interferometers used to detect gravitational waves. The fundamental properties of the interferometer are presented, including the power spectral density of the displacement noise.     

Ring resonator in a Sagnac interferometer as a birefringence magnifier

A novel birefringence magnification technique that uses a ring resonator in a Sagnac interferometer is proposed and demonstrated. An enhancement factor of 38 was obtained experimentally. The scheme can be used to increase measurement sensitivity to small birefringence and polarization mode dispersion and to decrease the threshold for nonlinear switching and laser mode locking by a Sagnac interferometer.     

Beyond the absorption-limited nonlinear phase shift with microring resonators

We show that the nonlinear phase shift produced by a ring resonator constructed from a given nonlinear optical material can be greater than the phase shift produced by a single pass through an infinite length of the same material when linear and nonlinear absorption are taken into consideration. The figure of merit (defined by the phase shift times the throughput) also improves for the ring resonator over that of the native nonlinear absorbing material. We finally show that these benefits of using the ring resonator as a nonlinear phase-shifting element can enhance the switching characteristics of a Mach-Zehnder interferometer.     

Four entangled photons generation using weak light and an all fiber optic scheme for multi-entangled photons generation

This paper proposes a simple scheme of four entangled photons generation using a pulse of weak light input into a Mach-Zehnder interferometer (MZI) incorporating a fiber optic ring resonator (FORR) without any optical pumping components included in the system. After a pair of entangled photon has been generated by a four-wave mixing of weak light pulse in the FORR [P.P. Yupapin, S. Suchat, Entangled photon generation using fiber optic Mach-Zehnder interferometer incorporating the nonlinear effect in a fiber ring resonator, Journal of Nanophotonics (JNP) 1 (2007) 013504], four and eight entangled photons can be performed. In application, the multi-entangled states can be formed using the appropriated coupling ratios into a fiber coupler. The effect of the entangled state walk-off along the optical fiber is discussed.     

Interferometric output coupling of ring optical oscillators

We demonstrate the successful deployment of an antiresonant ring (ARR) interferometer within a ring optical resonator and its use for absolute optimization of output power. The integration of the ARR interferometer in a folded arm of the ring oscillator provides continuously variable output coupling over broad spectral range and under any operating conditions. We demonstrate the technique using a picosecond optical parametric oscillator (OPO), where we show continuously adjustable output coupling and optimization of the output power for different pump power conditions, from 3.5 W to 13.5 W. By operating the OPO under an optimized output coupling at 14 W of pump power, we obtain >5 W of extracted signal power, more than 2.6 times that with a ~5% conventional output coupler. We also show that the inclusion of the ARR interferometer has no detrimental effect on the spatial, temporal, and spectral characteristics of OPO output.     

A Proposal and Demonstration for Photonic Generation of a Microwave Signal by Incorporating a Microring Resonator

A proposal for photonic generation of a microwave signal is presented by employing a dual wavelength erbiumdoped fibre ring laser. In the laser, a microring resonator is cascaded with a tunable bandpass filter to serve as a dual-wavelength selector, an unpumped polarization maintaining erbium-doped fibre is used as a saturable absorber. By replacing the microring resonator with a delay interferometer to verify the proposal, a wavelengthtunable dual wavelength single longitudinal mode laser is demonstrated, and a microwave signal at 10.01 GHz with a linewidth of less than 25 kHz is obtained by beating the two wavelengths at a photodetector.     

环形谐振器辅助马赫-曾德尔干涉仪型波长交错滤波器的研究

将环形谐振器与马赫-曾德尔干涉仪相结合,利用谐振器反馈回路引入的相位调节效应,选择合适的谐振器耦合角,设计出一种具有最大平坦滤波响应的环形谐振器辅助马赫-曾德尔干涉型波长交错滤波器.与普通马赫-曾德尔干涉型波长交错滤波器相比,不仅阻带抑制(>38dB)和过渡带滚降特性明显加强,而且在通带中心15 GHz范围,将色散降低到±10 ps/nm以内,从而可以有效避免对传输信号造成失真.在此基础上,进一步研究环周长(Lr)与马赫-曾德尔干涉臂长差(△L)之间的关系,指出波长交错滤波器奇偶输出端口的带宽分配比直接决定于Lr/△L,当调整Lr/△L=1/2,可以实现具有1;2非对称带宽分配特性的新型波长交错滤波器,为10 Gb/s向10 Gb/s 40 Gb/s系统升级提供一种简单、灵活的方式.     

Athermal silicon microring electro-optic modulator

We demonstrate a new class of passively temperature stabilized resonant silicon electro-optic modulators. The modulators consist of a ring resonator coupled to a Mach-Zehnder interferometer with tailored thermal properties. We demonstrate 2 GHz continuous modulation over a temperature range of 35 °C and describe the scalability and design rules for such a device.     

Impulse sensing with optical fiber interferometers

A method is proposed for using optical fiber interferometers to detect single energy impulses of very short time duration. The interferometer is used to measure the periodic strains induced in a mass that is shock-excited into mechanical oscillation by an energy impulse. This technique is demonstrated using an optical fiber ring resonator to measure the energy content of current pulses with durations in the microsecond range.     

Impulse sensing with optical fiber interferometers

A method is proposed for using optical fiber interferometers to detect single energy impulses of very short time duration. The interferometer is used to measure the periodic strains induced in a mass that is shock-excited into mechanical oscillation by an energy impulse. This technique is demonstrated using an optical fiber ring resonator to measure the energy content of current pulses with durations in the microsecond range.     

Electric Voltage Tuning of an All-fiber Mach-Zehnder Interferometer

The electric voltage tuning performance of an all-fiber Mach-Zehnder interferometer which has unequal arm-length is studied in this paper. This interferometer consists of two 3 dB fiber directional couplers, with one arm is affixed to a piezoelectric translators (PZT). When the voltage applied on the PZT changes, the output interferometric pattern will shift accordingly. The transmission period of the interferometer is 2.24 nm. When the direct current electric voltage changes from 28.7 volt to -28.7 volt, the pattern will shift for nearly one of its own period. The tuning sensitivity is about 0.038 nm/volt, and the linearity is 0.9991. Also, the relationship between the physical path length difference of the two arms and the interval of adjacent interferometric peaks is discussed. This component has potential important applications in electric sensing measurement and optical fiber communication field.     

A compact fir ring laser with open resonator and variable output coupling

We describe the design, construction and first experimental results with an open triangle FIR ring resonator with Michelson interferometer output coupling, which we combined with a Brewster-windowless 10W CO₂ pump laser to a compact laser package of 1m length. The achieved stability of power and frequency of this system is very high, typically on the order of ±0.01% over several hours and <20kHz per hour at 800GHz. For the design, we investigated the balance of all laser processes and determined the optimum dimensions for the open resonator cavity. This analysis is based on a radially homogenous overall laser model, including commonly accepted simplified rate equations together with molecular parameters for weak FIR laser lines. In accordance with the modelling the efficiency on the very most prominent lines is better than with conventional waveguide lasers, giving up to 4 times better efficiencies especially on lines with low absorption pump transitions. Several laser lines, however, have substantially enhanced pump thresholds on purely copropagating emission, suppressing laser operation below about 10W pump power threshold. We show that this can not be due to effects from the interferometer.     

Longitudinal-mode-partition noise in a semiconductor-laser-based interferometer

We observed a periodic intensity-noise variation in the output of a Mach-Zehnder interferometer as we changed the arm-length difference in the range of several millimeters. We found that the period of the variation coincided with that expected for the longitudinal-mode separation of the semiconductor laser. The origin of the huge excess noise of a bright fringe (approximately 30 dB above the shot-noise level) was the longitudinal-mode-partition noise that was due to the selective destructive interference of side modes.