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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - A Multi-Carrier Signals Generation Based on DPMZM In Parallel for THz Communication system
摘要： In this paper, a multi-carrier THz signals generation scheme is proposed and demonstrated. The scheme is based on DPMZM (dual-parallel Mach-Zehnder modulator) in parallel and recirculating frequency shifter (RFS). By optimizing all the sub-modulators embedded in the RFS, the multi-carrier signals with double frequency interval are generated. A theoretical analysis and simulation experiment is developed, the scheme can generate 20 carriers with 0.1THz frequency interval, and the side-mode suppression ratio (SMSR) is over 25dB.
关键词： side-mode suppression ratio,recirculating frequency shifter,multi-carrier THz signals,DPMZM
更新于2025-09-23 15:21:21
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Nonlinearity-compensation-free optical frequency domain reflectometry based on electrically-controlled optical frequency sweep
摘要： A nonlinearity-compensation-free optical frequency domain reflectometry (OFDR) scheme is proposed and experimentally demonstrated based on the electrically-controlled optical frequency sweep. In the proposed scheme, the linear frequency sweep light is generated by propagating an ultra-narrow-linewidth continuous-wave light through an electro-optic frequency shifter which consists of a dual-parallel Mach-Zehnder modulator and an electronic 90° hybrid, where the electro-optic frequency shifter is driven by a linear frequency modulated signal generated by a direct digital synthesizer. Experimental results show that the spatial resolution and signal-to-noise ratio (SNR) of the proposed OFDR scheme without the nonlinear phase compensation are comparable to those of the OFDR employing a commercial tunable light source (TLS), an auxiliary interferometer and a software-based nonlinear phase compensation method. The proposed OFDR scheme is helpful to reduce the complexity of optical structure and eliminate the difficulty of developing nonlinear phase compensation algorithm.
关键词： optical frequency domain reflectometry (OFDR),electro-optic frequency shifter,Dual-parallel Mach-Zehnder modulator,optical fiber sensor
更新于2025-09-23 15:19:57
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Acousto-optic modulators for a controlled frequency shift of light beams in optical and microwave cold-atom frequency standards
摘要： A series of specialised acousto-optic modulators/frequency shifters based on paratellurite (TeO2) single crystals is developed for systems of laser cooling and frequency stabilisation of laser sources in optical and microwave frequency standards based on cold strontium, rubidium and caesium atoms. The methods of calculation and optimisation of the main parameters of acousto-optic modulators are considered; their basic technical characteristics are experimentally investigated in the spectral range of optical radiation 460 – 900 nm and in the frequency shift range of 5 – 400 MHz. The modulators have a high diffraction efficiency, low power consumption and the ability to work with linearly and randomly polarised optical radiation.
关键词： frequency shifter,modulator,acousto-optic diffraction,frequency stabilisation,laser cooling,frequency shift,frequency standards
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Dual-Comb Spectroscopy using a Single Frequency-Shifting Loop
摘要： Dual-comb spectroscopy (DCS) is a multi-heterodyne interferometric technique that employs two optical frequency combs (OFCs) with different line spacing. When DCS is carried out with a pair of mode-locked OFCs, the need of a tight phase locking between them leads to sophisticated hardware and/or software implementations [1]. A strategy to simplify the DCS architecture, demonstrated with several comb modalities, is the use of a bidirectional laser cavity to produce two counter-propagating combs, each one having different line spacing [2,3]. Alternatively, but offering much more flexibility on the mode separation, electro-optic (EO) frequency combs can also be used for carrying out DCS. In that DCS scheme, both EO combs are fed by a single cw laser, which ensures by default a high degree of mutual coherence between them [4]. In the same vein, but comparatively much less exploited, frequency-shifting loops (FSLs) are also an easily implementable comb platform. Based on the recirculation of light in a loop containing an acousto-optic frequency shifter (AOFS), FSLs are capable of producing spectra with hundreds or even thousands of lines, without resorting to non-linear broadening or optimized fast driving electronics [5]. Recently, we have demonstrated DCS using two different FSLs [6]. However, this system requires the use of a low-bandwidth stabilization system to compensate for the uncorrelated fluctuations between the two combs, a requirement also found in other DCS schemes, and necessary for increasing the acquisition time (and, hence, the measurement signal-to-noise ratio) beyond the ms time scale. To improve the mutual coherence of the two OFCs, we present a bidirectional FSL that generates in the same optical loop two counter-propagating OFCs (called acousto-optic OFCs), with a tunable line spacing difference, as shown in Fig. 1a. The FSL is composed of three bidirectional elements: a frequency shifter that imparts a different frequency shift depending on the light direction, an optical amplifier (EDFA) and a tunable band-pass filter (BPF). The interference between the two acousto-optic OFCs produces a RF comb, whose bandwidth and flatness can be controlled through the parameters of the FSL (Fig. 1b). In order to test our setup, we performed molecular spectroscopy of a HCN absorption line, as can be observed in Fig. 1c. While much simpler, our system performs similarly to the technique that utilizes two different FSLs with a stabilization mechanism [6]. The presented bidirectional FSL is a compact and flexible scheme for DCS. Apart from avoiding duplication of the FSL, it provides common noise rejection between the two generated combs, allowing us to reach acquisition times up to the second scale. In addition, a pair of counter-propagating trains of optical pulses could also be generated by exploiting the temporal Talbot effect [5]. All these features make our system a powerful platform for multi-heterodyne interferometry, including molecular spectroscopy, distance ranging and fiber sensing.
关键词： Dual-comb spectroscopy,multi-heterodyne interferometry,acousto-optic frequency shifter,frequency-shifting loops
更新于2025-09-12 10:27:22