Vernier effect of fiber interferometer based on cascaded PANDA polarization maintaining fiber

This Letter shows the Vernier effect based on two segments of PANDA polarization maintaining fiber(PMF),whose lengths are 28 and 23 cm, respectively. The two PMFs are spliced together, and the angle between the fast axes is set to 45°. This cascaded PMF is inserted in a Sagnac loop to form an interferometer that can generate the Vernier effect. The spectrum consists of finesse fringe and envelope and realizes simultaneous measurement of strain and temperature. The envelope can provide strain and temperature sensitivities of 58.0 pm/με and -1.05 nm/℃. The finesse fringe provides sensitivities of 5.9 pm/με and -1.36 nm/℃.     

一种热光可调谐级联微环滤波器的理论分析

根据Vernier效应可大幅度提高滤波器自由光谱范围和调谐范围,设计了一种热光可调谐级联微环滤波器. 利用传输矩阵方法和有限元方法从理论上计算了对于第一级微环半径为48 μm,第二级半径为50 μm的级联微环滤波器的自由光谱范围和调谐范围可以达到75.6 nm,而功耗仅为103.1 mW,这是目前为止我们 所知的基于微环谐振腔的硅基热光可调谐滤波器中最大的自由光谱范围和在如此低功耗下最大的调谐范围. 利用有限元方法,还计算了半径为50 μm微环的热光调谐响应时间,上升沿时间为3.5 μs,下降沿时间仅为0.8 μs.     

Demonstration of a directed optical decoder using two cascaded microring resonators

We propose and demonstrate a directed optical decoder that can perform the decoding function from a two-bit electrical signal to a four-bit optical signal based on two cascaded microring resonators. We use two electrical signals regarded as a two-bit electrical signal to modulate the two microring resonators through the thermo-optic effect and four optical signals regarded as a four-bit optical signal appear at the output ports, respectively. The device operating at 10?kbps is demonstrated.     

A large bandwidth photonic delay line using passive cascaded silicon-on-insulator microring resonators

This paper investigated the design and the characterization of a photonic delay line based on passive cascaded silicon-on-insulator (SOI) microrings.We considered the compromise of group delay,bandwidth and insertion loss.A 3-stage double channel side-coupled integrated spaced sequence of resonator (SCISSOR) device was optimized by shifting the resonance of each microring and fabricated with electron beam lithography and dry etching.The group delay was measured to be 17 ps for non-return-to-zero signals at different bit rates and the bandwidth of 78 GHz was achieved.The experiment result agreed well with our simulation.     

Highly-sensitive silicon-on-insulator sensor based on two cascaded micro-ring resonators with vernier effect

A highly-sensitive integrated optical biosensor based on two cascaded micro-rings resonator (MRR) is investigated theoretically and experimentally. The free spectral ranges (FSRs) of two cascaded micro-rings are designed to be slightly different in order to generate Vernier effect. A preliminary investigation of our sensor with a Q factor of 2 × 10⁴ using different ethanol concentrations shows that the Vernier effect can improve the sensitivity to 1300 nm per refractive index unit (RIU), compared to 62 nm/RIU for a single ring sensor. The sensor also has a large measurement range of refractive index change up to 1.15 × 10^− 2 RIU. It can be useful for low-cost and highly-sensitive optical biosensor system.     

Highly sensitive Si nanowire-based optical sensor using a Mach-Zehnder interferometer coupled microring

A Mach-Zehnder interferometer (MZI) coupled microring is demonstrated experimentally to obtain a high sensitivity as well as a large range for measuring change in refractive index. For the present MZI-coupled microring, there is a major resonance wavelength with a high extinction ratio (16-36 dB) in a very large wavelength span. Consequently, a very large quasi-free spectral range (>120 nm) is achieved, which helps to obtain a large measurement range. The MZI-coupled microring sensor is used for measuring the change of the ambient refractive index ranging from 1.0 to 1.538, and the sensitivity is as high as 111 nm/refractive index unit.     

Optical fiber strain sensor using fiber resonator based on frequency comb Vernier spectroscopy

A novel (to our best knowledge) optical fiber strain sensor using a fiber ring resonator based on frequency comb Vernier spectroscopy is proposed and demonstrated. A passively mode-locked optical fiber laser is employed to generate a phased-locked frequency comb. Strain applied to the optical fiber of the fiber ring resonator can be measured with the transmission spectrum. A good linearity is obtained between displacement and the inverse of wavelength spacing with an R(2) of 0.9989, and high sensitivities better than 40 pm/με within the range of 0 to 10 με are achieved. The sensitivity can be proportionally improved by increasing the length of the optical fiber ring resonator.     

Coupling between microring resonators in presence of Kerr effect

The high degree of intensity values in microring resonators needs a careful treatment of nonlinear phenomena. Nonlinear effects are analyzed in coupling problem of ring-ring directional couplers. It has been observed that the nonlinearity affects the coupling device dramatically, and can be used as controlling techniques in such as coupled resonator optical waveguides.     

Remote fiber sensor based on cascaded Fourier domain mode-locked laser

We propose a high-speed remote fiber Bragg grating (FBG) sensor interrogation system based on a 1.3-μm cascaded Fourier-domain mode-locked (FDML) laser. It consists of multiple FBGs connected to an optical circulator in the laser cavity. The cascaded FDML laser with these multiple FBGs is operational when the scanning frequency of the fiber Fabry-Perot tunable filter matches the fundamental frequency of the laser cavity. Each FBG provides a separate laser cavity for the FDML laser. The scanning frequencies of each laser cavity are 30.5314, 31.5393, 32.7108, and 33.8023 kHz. Using the cascaded FDML laser, we measure the performance of the long-distance static strain FBG sensor interrogation system in both the time and spectral domains. The slope coefficients of the measured relative wavelength difference and the relative time delay from the static strain are found to be 0.95 pm/μstrain and 0.15 ns/μstrain, respectively. We also demonstrate the dynamic response of the interrogation system with 80-Hz modulation strain using the cascaded FDML laser. Thus, an FBG sensor interrogation system for high-speed and high-sensitivity long-distance monitoring systems can be realized using a cascaded FDML laser.     

Integrated lithium niobate single-mode lasers by the Vernier effect

Microcavity lasers based on erbium-doped lithium niobate on insulator(LNOI), which are key devices for LNOI integrated photonics, have attracted significant attention recently. In this study, we report the realization of a C-band single-mode laser using the Vernier effect in two coupled erbium-doped LNOI microrings with different radii under the pump of a 980-nm continuous laser. The laser, operating stably over a large range of pumping power, has a pump threshold of about 200 μW and a side-mode suppression ratio exceeding 26 dB. The high-performance LNOI single-mode laser will promote the development of lithium niobate integrated photonics.     

Analysis of microring filter with two embedded microring

In this paper, a microring resonator with two embedded microring (MRTEM) has been presented and studied theoretically. Transfer matrix method (TMM) has been used to simulate MRTEM and analyze the relations between add/drop spectrum and embedded microring arrangements. Three kinds of embedded microring arrangements have been proposed and analyzed by TMM. The theoretical and simulation results show that the Q factor of our structure is higher than that of traditional microring structure and the spectrum of MRTEM is independent on embedded arrangements.     

FP cavity and FBG cascaded optical fiber temperature and pressure sensor

A fiber Bragg grating(FBG) and Fabry–Perot(FP) cavity cascaded fiber sensing system was manufactured for temperature and pressure sensing. Temperature sensing as high as 175°C was performed by an FBG for the linear variation of an FBG wavelength with temperature. After the temperature was sensed, the demodulation system can find the original FP cavity length and its pressure and cavity length correlation coefficient; thus, the ambient pressure would be calculated. The sensing pressure can be as high as 100 MPa with a repeatability of 1/10,000 and high stability. This kind of fiber sensor has been used in the Shengli Oil Field.     

Proposal for loadable and erasable optical memory unit based on dual active microring optical integrators

A novel approach for loadable and erasable optical memory unit based on dual microring optical integrators is proposed and studied. The optical integrator, which can generate an optical step function for data storing, is synthesized using active media for loss compensation and a tunable phase shifter for data reading at any time. The input data into the memory is return-to-zero (RZ) signal, and the output data read from the memory is also RZ format with a narrower pulse width. An optical digital register based on the proposed optical memory unit is also investigated and simulated, which shows the potential for large scale data storage and serial-to-parallel data conversion. A great number of such memory units can be densely integrated on a photonic circuit for future large scale data storage and buffer.     

All-optical NRZ-to-AMI conversion using linear filtering effect of silicon microring resonator

We experimentally demonstrate 10-Gb/s format conversion from non-return-to-zero （NRZ） to alternatemark-inversion （AMI） using the linear filtering effect of silicon microring resonator. Our discussion and analysis in simulation further show that a 10-Gb/s AMI signal with good quality can be obtained by a resonator with a notch depth larger than 25 dB when the 3-dB bandwidth is 0.4 nm.     

All-optical NRZ-to-AMI conversion using lising linear filtering effect of silicon microring resonartor

We experimentally demonstrate 10-Gb/s format conversion from non-return-to-zero (NRZ) to alternate mark-inversion (AMI) using the linear filtering effect of silicon microring resonator. Our discussion and analysis in simulation further show that a 10-Gb/s AMI signal with good quality can be obtained by a resonator with a notch depth larger than 25 dB when the 3-dB bandwidth is 0.4 nm.     

Broadening free spectral range of an evanescent-wave pumped Whispering-Gallery-Mode fibre laser by Vernier effect

Evanescent-wave pumping scheme has been successfully used to excite Whispering-Gallery-Mode fibre laser. The free spectral range of the lasing spectrum from a single optical fibre is found to be very narrow, to increase the free spectral range, a coupled cylinder-cavity structure has been fabricated by binding two bare optical fibres together, based on Vernier effect, the free spectral range of the coupled cylinder-cavity structure has been effectively broadened over 15 times compared with that of a single optical fibre. The measured free spectral ranges for both coupled cylinder-cavity structure and the single optical fibre are consistent with theoretical prediction.     

A comparative study on dual colour soft aperture cascaded second-order mode-locking with different nonlinear optical crystals

A comparative study in terms of optimized output power and stability is made on cascaded second-order nonlinear optical mode-locking with KTP, BBO and LBO crystals for both 1064 nm and 532 nm. Large nonlinear optical phase shift achieved in a non-phase-matched second harmonic generating crystal, is transformed into amplitude modulation through soft aperturing the nonlinear cavity mode variation at the laser gain medium to mode-lock a Nd:YVO4 laser. The laser delivers stable dual wavelength cw mode-locked pulse train with pulse duration 10.3 ps and average power of 1.84 W and 255 mW at 1064 nm and 532 nm respectively for the optimum performance in type-II KTP crystal. The exceptional stability achieved with KTP is accounted by simulating the mode-size variation with phase mismatch.     

Chaotic dynamics of semiconductor microring lasers

The complexity and dynamics of chaotic attractors generated in an InGaAsP-InP microring laser are calculated and evaluated by using a multimode rate equation model. Chaos originates from the continuous mutual injections from each mode to the other because of the bus waveguide's residual reflectivity at high values of the injection current. The data analysis of the filtered output power reveals high-dimensional chaos, and phase-dependent behavior is demonstrated.     

Coupling of concentric semiconductor microring lasers

Coupling between whispering-gallery modes of concentric microcavity lasers was analyzed, and a closed-form three-dimensional vectorial solution for the coupled fields was obtained. Experiments performed with concentric gain-guided vertical cavity ring lasers resulted in regimes of resonant coupling in good agreement with the theory.     

Model of Vernier devices in silicon-on-insulator technology

In order to increase the number of channels that could be multiplexed or demultiplexed in the dense wavelength division multiplexed (DWDM) system based on the resonators on silicon-on-insulator (SOI) technology, the Vernier effect in the series-coupled racetrack resonators is presented to extend the free spectral range (FSR) of the DWDM systems. A method is developed based on a matrix approach to simulate Vernier devices. A three-dimensional full vectorial finite difference (FVFD) model, specifically suited for high index contrast and smaller size waveguides, for example, a waveguide in SOI technology, is developed to obtain the properties of a waveguide. Finally, the Vernier effect in the two series-coupled racetrack resonators is experimentally verified with an improved FSR and interstitial resonance suppression.