Optical Fiber Ring Laser Research Articles

Adaptive Fiber Ring Laser Based on Tapered Polarization Maintaining Fiber in Sagnac Loop for Temperature and Salinity Sensing

An optical fiber ring laser (FRL) cavity-based sensitive temperature and salinity sensor is proposed and experimentally demonstrated. The sensor consists of a Sagnac loop with a waist of 15 µm and a total length of 30 cm made of tapered polarization-maintaining fiber (PMF). Sagnac loop dual parameter sensing was theoretically modeled and presented. The salinity sensitivity of 0.173 nm/‰ was made possible by the efficient interaction between the tapered PMF cladding mode and the external refractive index. In addition, temperature sensitivity of 0.306 nm/°C was achieved through ultrahigh birefringence of PMF. Apart from that, the previous sensing system used a broadband light source (BBS) as the input light, resulting in a wide bandwidth and a poor signal-to-noise ratio (SNR). The Sagnac loop integrated into the FRL system can achieve a high SNR of approximately 50 dB and a narrow bandwidth of 0.15 nm while serving as the filter and sensor head. Additionally, the developed sensor has the advantages of simple design, low cost, and easy fabrication. It can also extend sensing distance indefinitely within a given range, which is anticipated to have positive effects on the testing of marine environments in laboratories.

Fiber Optic Electric Field Intensity Sensor Based on Liquid Crystal-Filled Photonic Crystal Fiber Incorporated Ring Laser

Optical fiber sensors are of splendid strength for electrical field intensity sensor due to characteristics including the immunity to electromagnetic interference, lightweight, high sensitivity, and large bandwidth. In this paper, we proposed an electric field intensity sensor based on Mach-Zehnder interferometer (MZI) based liquid crystal (LC) filled photonic crystal fiber (PCF) embedded in optical fiber ring laser (FRL). The air hole of PCF combines the LC and fiber core together. When LC is introduced into air holes, it can maintain the waveguide based on external parameters. The photonic bandgap effect significantly improved the sensitivity between light and external electrical field intensity. Thanks to the FRL demodulation, a high signal to noise ratio (SNR) spectrum about 35 dB is obtained. Besides, in comparison with traditional LC-PCF structures, the sensitivity of ours is as high as 1.1 nm/Vrms which is about twice than traditional sensors. At the same time, the stability of proposed sensor was verified which fluctuation was 0.15 nm around 2.5 hours. Therefore, our structure is expected to practical applications in remote electric field monitor and such electric modulate electro-optical devices.

Wavelength converter using a highly Er-doped optical fiber ring laser

This work presents an all-fiber wavelength converter based on a highly Er-doped fiber laser, which has been experimentally demonstrated. Frequencies from several kilohertz up to tens of gigahertz have been investigated. Making use of the gain competition in the amplifying medium, the wavelength conversion can be carried out over not only one lasing wavelength, but over several. These analyses have also been carried out for more than one all-fiber ring structure, demonstrating the viability of this wavelength converter. To the best of our knowledge, this is the first time an Er-doped fiber wavelength converter has been validated.

Remote PCF-based sensors multiplexing by using optical add–drop multiplexers

Abstract A 100 km remote PCF micro-displacement sensor multiplexing system based on optical add–drop multiplexers (OADMs) has been experimentally demonstrated. The PCF sensors are placed in an OADM bus structure which is illuminated by a home-made tunable fiber optic ring laser. Four micro-displacement photonic crystal fiber (PCF) sensors based on a suspended core fiber inserted into a Sagnac loop filter are multiplexed. Furthermore, being the first proposal to solve this issue in PCF sensor multiplexing structures, these sensors can be referenced with an extra wavelength.

Influence of the Frequency-chirp on Pulse in Passively Mode-locking Optical Fiber Ring Laser

We consider a model of a passively mode-locking fiber ring laser bult using a saturable absorber and a chirped fiber Bragg grating to balance dispersion and nonlinearity. The evolution of the slowly envelope of the optical field in a loop fiber subject to dispersion , Kerr nonlinearity, frequency- chirp and nonlinear absorption is given by the generalized complex Ginzburg-Landau equation. The influence of the frequency-chirp on the pulse is simulated and discussed, and the stationary conditions concerning the chirp parameter are found out for our laser.

Analysis of Output Characteristic for Fiber Bragg Gratings Laser

A spread equation of erbium-doped optical fiber laser was derived from the basic theory of laser. Then, the hypothesis of erbium-doped optical fiber ring laser was proposed. The special computation procedure and the theoretical arithmetic emulation of output characteristic for this laser were conducted by discussing the effect of the configuration. Moreover, this article further investigated the influence of the relationship between pumping and laser output, cavity distribution of gas gain, slope efficiency and the influence that the output coupling rate parameters having on the laser output of optical fiber laser.

Semiconductor Optical Amplifier (SOA)-Fiber Ring Laser and Its Application to Stress Sensing

We have developed a novel optical fiber ring laser using a semiconductor optical amplifier (SOA) as the gain medium, and taking advantage of polarization anisotropy of its gain. The frequency difference of the bi-directional laser is controlled by birefringence which is introduced in the ring laser cavity. The beat frequency generated by combining two counter-propagating oscillations is proportional to the birefringence, the fiber ring laser of the present study is, therefore, applicable to the fiber sensor. The sensing signal is obtained in a frequency domain with the material which causes the retardation change by a physical phenomenon to be measured. For the application to stress sensing, the present laser was investigated with a photoelastic material.

环形掺铒光纤激光器自混合散斑及动态目标距离测量

A new method of dynamic target distance measurement based on self-mixing speckle in an erbium-doped fiber-optic ring laser is studied. The model of self-mixing speckle measurement system is presented, and the theoretical analysis of the production of self-mixing speckle signal is also given. Through the experiments, the dynamic speckle signal is obtained. The spectrum energy density analysis is applied to the dynamic speckle signals, and a linear relationship between the spectrum energy density and the detection distance is obtained. The result shows that highly precise distance dynamic measurements can be performed by using self-mixing speckle and fiber laser.

Using Brillouin fiber-optic ring laser to provide base station with uplink optical carrier in a 10 GHz radio over fiber system

In this paper, a 10 GHz radio over fiber system is analyzed. The Brillouin fiber-optic ring laser is used in the center station (CS) to suppress the optical carrier for the modulation depth enhancement. Simultaneously, the Stockes wave induced by the Brillouin amplification injects and locks the Fabry-Perot (FP) laser to output a signal-mode optical source, which works as the uplink optical carrier.

环形腔掺铒光纤激光器的理论研究

环形腔掺铒光纤激光器的理论研究

Ring-laser gyroscope without the lock-in phenomenon

We theoretically and numerically study the effect of backscattering on rotating ring lasers by employing the Maxwell-Bloch equations. We show that frequency shifts due to the Sagnac effect incorporating the effect of backscattering can be observed without lock-in phenomenon, if the strength of backscattering originating in the bumps of the refractive index is larger than a certain value. It is also shown that the experimental results corresponding to the theoretical ones can actually be obtained by using a semiconductor fiber-optic ring laser gyroscope.

Semiconductor Optical Amplifier-Fiber Laser and Its Improvement for Sensor Application

We have developed a novel optical fiber ring laser using a semiconductor optical amplifier (SOA) as the gain medium, and taking advantage of polarization anisotropy of its gain. Since the frequency difference of the bi-directional laser is proportional to the introduced birefringence, the laser in the present study is applicable to a frequency-domain fiber sensor with the birefringent material. For the application the accuracy and stability of the beat signal frequency is important, but it was not sufficient because the polarization of the propagating light was not constant in the single-mode fiber (SMF) which was incorporated into the ring laser cavity. In order to reduce this ambiguity, we have improved the fiber ring laser by using polarization-maintaining fiber (PMF) and a PMF-coupler instead of SMF and a SMF-coupler. The linewidth of the beat signal has been narrowed and the accuracy of the beat signal frequency has been enhanced.

SOA-fiber ring laser and its application to electric field sensing in frequency domain

We have developed a novel optical fiber ring laser using a semiconductor optical amplifier (SOA) as the gain medium, and taking advantage of polarization anisotropy of its gain. The laser can control the oscillation frequency difference between two counterpropagating lights by incorporating a birefringent medium into the ring resonator. Since the frequency difference is proportional to the birefringence, it can be measured to detect the beat frequency generated by combining two counterpropagating lights and the laser can be applied to an optical fiber sensor whose detecting signal is in frequency domain. Electric field sensor was demonstrated with a lithium niobate crystal as a sensing probe.

Measuring optical fiber length by use of a short-pulse optical fiber ring laser in a self-injection seeding scheme

A method for measuring the length of an optical fiber by use of an optical fiber ring laser pulse source is proposed and demonstrated. The key element of the optical fiber ring laser is a gain-switched Fabry-Perot laser diode operated in a self-injection seeding scheme. This method is especially suitable for measuring a medium or long fiber, and a resolution of 0.1 m is experimentally achieved. The measurement is implemented by accurately determining the pulse frequency that can maximize the output power of the fiber ring laser. The measurement results depend only on the refractive index of the fiber corresponding to this single wavelength, instead of the group index of the fiber, which represents a great advantage over both optical time-domain reflectometry and optical low-coherence reflectometry methods.

새로운 스트레인 인가장치를 이용한 광섬유 링 레이저의 파장가변 특성

We fabricated a tunable fiber ring laser consisting of a novel strain device and fiber Bragg gratings. The lasing power and FWHM bandwidth of the optical fiber ring laser was -12dBm and 0.05nm respectively. The fiber ring laser was tuned as much as 10nm at a 8000.

Experimental observation of mode behavior in erbium-doped optical fiber ring laser

Two-polarization mode oscillation is observed in an erbium-doped optical fiber ring laser. This phenomenon was verified by the existence of the polarization hole burning effect in this optical fiber ring laser. The laser is a ring laser operating in the region of 1.55 μm, pumped by a 1.48 μm InGaAsP laser diode. Mode-hopping and mode-competition instabilities due to spatial hole burning and inhomogeneous spectral broadening were eliminated by using an ultra-narrow-bandwidth optical fiber Bragg grating and a polarization independent optical isolator. The oscillation in the two-polarization mode operation is remarkably stable at higher pump powers. The application of two-polarization mode oscillation for temperature sensing is described. The sensing is novel in that the change of double refraction with temperature and the frequency detection are combined. In this method, the detection sensitivity with temperature rise was about 100 Hz/°C at around 40°C.

Lock-in reduction technique for fiber-optic ring laser gyros

We have demonstrated a Brillouin fiber-optic gyro that utilizes push-pull phase modulation in the ring cavity to suppress frequency locking. This in-line modulation allows an all-fiber system with optical reciprocity. A tenfold reduction of the width of the lock-in range is observed experimentally.

Widely tunable semiconductor optical fiber ring laser

A wide tunable optical fiber ring laser with a diffraction grating as a tuning element is demonstrated. A wide tuning range over 100 nm is achieved using a high performance traveling-wave amplifier (TWA) as a gain medium. The TWA with a V-grooved inner stripe structure on a p substrate (VIPS structure) has a high peak gain over 30 dB and a broad gain width of 100 nm at 16 dB. The effects of the gain of TWA and the total loss of the external ring cavity on the tuning range are also discussed.