Fiber Fabry-Perot Tunable Filter Research Articles

Tunable erbium-doped fiber ring laser for applications of infrared absorption spectroscopy

We fabricate a low noise erbium-doped fiber ring laser that can be continuously tuned over 102nm by insertion of the fiber Fabry–Perot tunable filter (FFP-TF) in the ring cavity with a novel cavity structure and the optimal gain medium length. As an application of this fiber ring laser, we performed the absorption spectroscopy of acetylene (13C2H2) and hydrogen cyanide (H13C14N) and measure the absorption spectra of more than 50 transition lines of these gases with an excellent signal to noise ratio (SNR). The pressure broadening coefficients of four acetylene transition lines are obtained using this fiber ring laser and an external cavity laser diode.

Tunable S-band erbium-doped triple-ring laser with single-longitudinal-mode operation

We propose and demonstrate a tunable and stable single-longitudinal-mode (SLM) erbium fiber laser with a passive triple-ring cavity structure in S-band operation. The proposed laser is fundamentally structured by using three different lengths of ring cavities, which serve as the mode filters. When a mode-restricting intracavity fiber Fabry-Perot tunable filter (FFP-TF) is combined, the proposed resonator can guarantee a tunable and stable SLM laser oscillation. Moreover, the performances of the output power, wavelength stability, tuning range, and side-mode suppression ratio (SMSR) are studied.

Long-distance fiber Bragg grating sensor system with a high optical signal-to-noise ratio based on a tunable fiber ring laser configuration

A novel tunable fiber ring laser configuration with a combination of bidirectional Raman amplification and dual erbium-doped fiber (EDF) amplification is proposed for realizing high optical signal-to-noise ratio (SNR), long-distance, quasi-distributed fiber Bragg grating (FBG) sensing systems with large capacities and low cost. The hybrid Raman-EDF amplification configuration arranged in the ring laser can enhance the optical SNR of FBG sensor signals significantly owing to the good combination of the high gain of the erbium-doped fiber amplifier (EDFA) and the low noise of the Raman amplification. Such a sensing system can support a large number of FBG sensors because of the use of a tunable fiber Fabry-Perot filter located within the ring laser and spatial division multiplexing for expansion of sensor channels. Experimental results show that an excellent optical SNR of approximately 60 dB has been achieved for a 50 km transmission distance with a low Raman pump power of approximately 170 mW at a wavelength of 1455 nm and a low EDFA pump power of approximately 40 mW at a wavelength of 980 nm, which is the highest optical SNR achieved so far for a 50 km long FBG sensor system, to our knowledge.

Fourier Domain Mode Locking (FDML): A new laser operating regime and applications for optical coherence tomography

We demonstrate a new technique for frequency-swept laser operation--Fourier domain mode locking (FDML)--and its application for swept-source optical coherence tomography (OCT) imaging. FDML is analogous to active laser mode locking for short pulse generation, except that the spectrum rather than the amplitude of the light field is modulated. High-speed, narrowband optical frequency sweeps are generated with a repetition period equal to the fundamental or a harmonic of cavity round-trip time. An FDML laser is constructed using a long fiber ring cavity, a semiconductor optical amplifier, and a tunable fiber Fabry-Perot filter. Effective sweep rates of up to 290 kHz are demonstrated with a 105 nm tuning range at 1300 nm center wavelength. The average output power is 3mW directly from the laser and 20 mW after post-amplification. Using the FDML laser for swept-source OCT, sensitivities of 108 dB are achieved and dynamic linewidths are narrow enough to enable imaging over a 7 mm depth with only a 7.5 dB decrease in sensitivity. We demonstrate swept-source OCT imaging with acquisition rates of up to 232,000 axial scans per second. This corresponds to 906 frames/second with 256 transverse pixel images, and 3.5 volumes/second with a 256x128x256 voxel element 3-DOCT data set. The FDML laser is ideal for swept-source OCT imaging, thus enabling high imaging speeds and large imaging depths.

TUNABLE FIBER FABRY-PEROT FILTER FOR OPTICAL CARRIER-SUPPRESSION AND SINGLE-SIDEBAND MODULATION IN RADIO OVER FIBER LINKS

A novel method of simultaneous realization of optical carrier-suppression and single-sideband modulation using fiber Fabry-Perot tunable filter is presented. In order to enhance transmission performance of radio over fiber links, we use a fiber Fabry-Perot tunable filter to filter out one sideband as well as suppress the optical carrier power. The results demonstrate 20.5dB and 14.2dB improvement in the signal noise ratios when 18GHz and 10GHz microwave signals carrying 5Mbit/s quadrature-phase-shift-keyed (QPSK) format data is transmitted over 35 km single mode fiber, respectively.

A tunable erbium-doped fiber ring laser with power-equalized output

We propose and demonstrate a tunable erbium-based fiber ring laser with power-equalized output. When a mode-restricting intracavity fiber Fabry-Perot tunable filter (FFP-TF) is combined, the proposed resonator can guarantee a tunable laser oscillation. This proposed laser can obtain the flatter lasing wavelength in an effectively operating range of 1533.3 to 1574.6 nm without any other operating mechanism. Moreover, the performances of the output power, wavelength tuning range, and side-mode suppression ratio (SMSR) were studied.

Amplified, frequency swept lasers for frequency domain reflectometry and OCT imaging: design and scaling principles

We demonstrate a high-speed, frequency swept, 1300 nm laser source for frequency domain reflectometry and OCT with Fourier domain/swept-source detection. The laser uses a fiber coupled, semiconductor amplifier and a tunable fiber Fabry-Perot filter. We present scaling principles which predict the maximum frequency sweep speed and trade offs in output power, noise and instantaneous linewidth performance. The use of an amplification stage for increasing output power and for spectral shaping is discussed in detail. The laser generates ~45 mW instantaneous peak power at 20 kHz sweep rates with a tuning range of ~120 nm full width. In frequency domain reflectometry and OCT applications the frequency swept laser achieves 108 dB sensitivity and ~10 mum axial resolution in tissue. We also present a fast algorithm for real time calibration of the fringe signal to equally spaced sampling in frequency for high speed OCT image preview.

Swept source optical coherence tomography using an all-fiber 1300-nm ring laser source

The increased sensitivity of spectral domain optical coherence tomography (OCT) has driven the development of a new generation of technologies in OCT, including rapidly tunable, broad bandwidth swept laser sources and spectral domain OCT interferometer topologies. In this work, the operation of a turnkey 1300-nm swept laser source is demonstrated. This source has a fiber ring cavity with a semiconductor optical amplifier gain medium. Intracavity mode selection is achieved with an in-fiber tunable fiber Fabry-Perot filter. A novel optoelectronic technique that allows for even sampling of the swept source OCT signal in k space also is described. A differential swept source OCT system is presented, and images of in vivo human cornea and skin are presented. Lastly, the effects of analog-to-digital converter aliasing on image quality in swept source OCT are discussed.

Wavelength-tunable add-drop multiplexers using fiber Fabry-Pe´rot tunable filters for bidirectional wavelength-division multiplexing networks

A novel wavelength-tunable add-drop multiplexer (ADM) us- ing fiber Fabry-Perot tunable filters (FFP-TFs) for the bidirectional wave- length division multiplexing (WDM) network is proposed and demon- strated. The wide tuning range, low loss, and low polarization dependence properties of the FFP-TFs are used for the ADM operation. The experimental results show that the wavelength tuning range of this wavelength-tunable ADM can be up to 40 nm. The bit-error-rate perfor- mance of the dropped and pass-through channels for a 2.5 Gbit/s sys- tem shows the feasibility of ADM. © 2004 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1787835)

Discretely tunable erbium-doped fiber ring laser selecting ITU-T grids of 273 channels � 50-GHz spacing in C- and L-band regions

We report the fabrication of a discretely tunable erbium-doped fiber ring laser with a novel scheme that can select ITU-T grids of 50-GHz spacing in both C and L bands. Wavelength selections of 273 channels are demonstrated with a signal to source spontaneous emission ratio of 60 dB/nm and excellent power flatness over 111-nm bandwidth. This was realized by incorporating both a solid Fabry–Perot interferometer and a fiber Fabry–Perot tunable filter into the ring laser. To our knowledge, our experimental result has the widest tuning range ever reported for a discretely tunable fiber laser with 50-GHz channel spacing that matches the ITU-T grids and is the first equipment that can operate in both C and L bands.

A novel wavelength switchable fiber laser source and its application in photonics beamforming for optically controlled phased array antenna

A novel wavelength-switchable fiber laser source that can individually scan 14 required wavelengths within 40 ms, and its application in photonics true time delay beamforming is presented in this paper. The laser source is constructed using a unidirectional fiber ring cavity, a tunable fiber Fabry–Perot filter and two cascaded sampled fiber Bragg gratings with the wavelength spacing of 1.6 nm. A five-channel true-time-delay system using the proposed fiber laser source cooperating with a single-mode fiber and four chirped-grating-based is constructed and demonstrated for the application of phased array antenna beam steering. Continuous beam steering at the microwave frequency up to 20 GHz has been achieved.

Effects of active fiber length on the tunability of erbium-doped fiber ring lasers

We numerically investigate the effects of the active fiber length on the tunability of erbium-doped fiber ring lasers for the cases of with and without pair-induced quenching (PIQ). The numerical results are confirmed by experiments. We have found that the tuning range shifts from C-band to L-band with an increase in the active fiber length. A maximum tuning range of over 100 nm, covering both the C- and L-band, can be achieved with an optimized active fiber length. It is also found that the PIQ is favorable for Lband lasing though it reduces the output power and degrades the power flatness. Using these findings, a novel method employing active fiber length switching is proposed to extend the tuning range of the laser, which is only limited by the free spectral range (FSR) of the tunable filter. A large tuning range of 102 nm is obtained using a tunable fiber Fabry-Perot filter with an FSR of 75 nm.

파장가변 광섬유 링 레이저를 이용한 아세틸렌(13C2H2) 분광

본 연구에서는 C-밴드와 L-밴드 파장(1525 nm-1625 nm)에서 파장 변화가 가능한 광섬유 링 레이저를 제작하고, 이를 이용하여 아세틸렌 분자 전이선에 대한 분광연구를 수행하였다. 제작된 광섬유 링 레이저는 공진기 내부에 FFP-TF(Fiber Fabry-Perot Tunable Filter)를 이용하여 약 102 nm(1510.4-1612.6 nm)의 범위에서 파장을 연속 가변할 수 있었다. 광섬유 링 레이저의 파장가변특성을 이용하여 C-밴드(1525-1565 nm)에서 흡수선이 많은 아세틸렌(<TEX>$^{13}$</TEX>C<TEX>$_2$</TEX>H<TEX>$_2$</TEX>)분자에서 50개 이상의 전이선에 대하여 높은 신호대 잡음비를 갖는 흡수 스펙트럼을 측정하였다. We fabricated erbium-doped fiber ring laser with a new structure that can operate in C- & L-band wavelength region. The wave-length of the laser can be tuned continuously over 102 nm between 1510.4-1612.6 nm by insertion of the fiber Fabry-Perot tunable filter (FFP-TF) in the ring cavity. By use of the wavelength tunable characteristics of our fiber laser, we measured absorption spectra of more than fifty transition lines of the acetylene (<TEX>$^{13}$</TEX> C<TEX>$_2$</TEX>H<TEX>$_2$</TEX>) molecule with high signal to noise ratio (SNR).

Characteristics of a wavelength-switching fiber laser source

The static and switching characteristics of a novel wavelength-switching fiber laser source for an optically controlled phased-array antenna (OCPAA) has been studied experimentally. The laser source was configured within a unidirectional ring cavity, with a tunable fiber Fabry-Perot filter, containing two sampled fiber Bragg gratings with a wavelength spacing of about 1.6 nm. It can individually scan the 25 required wavelengths in the fiber Bragg grating array in the OCPAA within 0.08 s. The switching speed, limited by relaxation oscillation, was analyzed. The polarization insensitivity of the ring cavity made the laser output at each wavelength very stable. Side-mode suppression ratios greater than 40 dB for each lasing wavelength were realized.

Wavelength-switching fiber laser for optically controlled phased-array antenna

A novel wavelength-switching fiber laser source for optically controlled phased-array antenna (OCPAA) is presented for the first time. It can individually scan 25 required wavelengths of the fiber Bragg grating (FBG) array in the OCPAA within 80 ms. The laser source was configured within a unidirectional ring cavity, with a tunable fiber Fabry–Perot filter (FFPF), and two sampled fiber Bragg gratings (SFBG) having a wavelength spacing of 1.6 nm. The average output power of 1.3 mW and the side-mode-suppression ratio of greater than 40 dB for each wavelength were realized. The temporal wavelength-switching characteristics, limited by the relaxation oscillation of the laser and related to the losses and the pump power in the ring cavity, were studied.

A Pressure Sensor Using Fiber Bragg Grating

A pressure sensor utilizing a fiber Bragg grating (FBG) has been demonstrated. An FBG interrogation system consisting of a fiber Fabry-Perot tunable filter detects the shift in the reflected wavelength when a range of force was applied perpendicularly to a bare FBG, resulting in a nonlinear response. When the FBG was embedded within some carbon fiber material, the test results show an excellent linearity between the wavelength shift and the applied force. Sensing force of up to 60N has been demonstrated without causing deformation to the FBG. The pressure sensor has a sensitivity of 1pm (equivalent to ∼0.8μ∈).

High-speed liquid crystal fiber Fabry-Perot tunable filter

We report a liquid-crystal fiber Fabry-Perot tunable filter (LC-FFP-TF) with fast tuning (<33 μs) over a 0.4-12 nm wavelength range centered at 1550 nm, at a temperature of 35/spl deg/C, using a commercially available electroclinic LC material, BDH764E. Typically, the fall time of the LC-FFP-TF is over an order of magnitude shorter than the rise time. For the first time to our knowledge, switching between two discrete wavelengths was demonstrated using an LC-FFP-TF.

Polarization-maintaining fiber Fabry–Perot tunable filters

We report what are to our knowledge the first high-performance polarization-maintaining single-mode fiber Fabry-Perot tunable filters. These filters simultaneously exhibited a loss of <2.5 dB, a finesse between 150 and 310, and an extinction ratio of >30 dB. A unique fabrication technique is developed that utilizes the tunability and the polarization resonance splitting inside the filter to align the birefringent axes at a pigtail-cavity joint. A general criterion is established for aligning polarization-maintaining fibers with elliptical inputs.

1.2 Gb/s closely-spaced FDMA-FSK direct-detection star network

For the frequency-division-multiple-access-frequency-shift-keying (FDMA-FSK) network, the FSK signal is converted to amplitude-shift-keyed (ASK) format by a tunable fiber Fabry-Perot (FFP) filter that acts simultaneously as a demodulator and demultiplexer. Frequency-tunable two-electrode distributed-feedback (DFB) laser transmitters produce distorted FSK spectra due to nonuniform FM response for modulation frequencies above approximately 200 Mb/s. The frequency-domain properties of the laser are related directly to the time-domain properties of the transmitted data stream. The critical dependence on the FFP passband width and center frequency location for undistorted signal recovery is shown. By optimizing these parameters, the data transmission rate can be increased while keeping the power penalty due to signal distortion below 1 dB.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

FSK with direct detection in optical multiple-access FDM networks

High-performance optical data networks of the future may interconnect hundreds of users at gigabit rates for a reasonable cost. A novel approach is described that utilizes a passive star coupler for distribution, a multiplicity of frequency-shift keyed (FSK) tunable lasers to provide a frequency division multiplexed (FDM) network, and a tunable optical fiber Fabry-Perot filter to select the channels and convert the FSK signal to ASK (amplitude-shift keying) for direct detection. The design of high-speed FDM-FSK direct detection networks and the performance of critical devices, such as tunable FM lasers, tunable filters, integrated star couplers, and optical amplifiers, are reviewed and discussed. >