Multi-wavelength fiber ring laser based on a sampled chirped fiber Bragg grating with a hybrid gain medium

The novel multi-wavelength fiber ring laser based on a sampled chirped fiber Bragg grating with a single SOA or a hybrid gain medium is demonstrated, respectively. In case of a hybrid gain medium, the SMSR improvement of ~ 5 dB was obtained when compared with the system with a single SOA. The proposed fiber laser offers advantages such as simple structure, low loss, multi-wavelength lasing lines with moderate output power.     

Single-longitudinal-mode erbium-doped fiber laser with novel scheme utilizing fiber Bragg grating inside ring cavity

In this paper, we experimentally investigate a single-longitudinal-mode (SLM) S-band erbiumdoped fiber (EDF) laser with dualring scheme using a S-band fiber Bragg grating (FBG) inside the gain cavity to restrict the lasing mode. The proposed laser is constructed by two-ring cavities serving as the mode filters. The FBG inside the proposed laser scheme can retrieve the SLM operation. Moreover, the output performance of the proposed fiber laser is also analyzed and discussed.     

Wavelength-switchable erbium-doped fiber ring laser combined with a Fabry-Perot laser diode and a sampled grating

We present a wavelength-switchable erbium-doped fiber ring laser consisting of an anti-reflection coated Fabry-Perot laser diode (FP-LD) and a sampled fiber Bragg grating (SFBG). The wavelength switching is obtained easily by the shift of FP mode with respect to the reflection peaks of the SFBG. The proposed laser apparatus not only simultaneously emits two wavelengths but also switches between the two wavelengths by adjusting the modes of FP-LD with a change of the injection current of the FP-LD as little as ∼1 mA. The proposed wavelength-switchable erbium-doped fiber ring laser exhibits high laser performance with side-mode suppression ratio (SMSR) ?50 dB.     

Multiwavelength pulse generation in semiconductor-fiber ring laser using a sampled fiber grating

A novel multiwavelength scheme has been demonstrated using a sampled fiber grating in semiconductor-fiber ring laser. By using semiconductor optical amplifier as an inhomogeneously broadened gain medium, three wavelength channels of 10 GHz are simultaneously generated. The number of the lasing channels can be changed through the polarization state adjustment in the cavity.     

Optimization of reflection spectra for phase-only sampled fiber Bragg gratings

In this paper, the reflection spectra of a phase-only sampled fiber Bragg grating is obtained by optimizing its phase profile. The standard simulated annealing method is improved for optimization, and superior phase profiles which contain as few segments as possible per sampling period are obtained for 8, 16 and 32 identical channels. As very well known, increased number of WDM channels results in higher grating length and refractive index modulation amplitude. It is observed that application of these phase profiles limits the increases in both of these parameters considerably.     

Continuously spacing-tunable multiwavelength semiconductor-optical-amplifier-based fiber ring laser incorporating a superimposed chirped fiber Bragg grating

We investigate a flexibly tunable multiwavelength semiconductor-optical-amplifier-based fiber ring laser with continuous wavelength spacing controllability incorporating a superimposed chirped fiber Bragg grating (CFBG). The wavelength spacing of a superimposed CFBG can be continuously controlled by symmetrically modifying the chirp bandwidth of the grating with the specially designed apparatus. We achieve a wide and continuous tuning range of the wavelength spacing from 0.35 to 0.78 nm. The continuous tunability of the wavelength spacing is measured to be ~ +/-0.033 nm/mm. By controlling the reflection bandwidth of the tunable CFBG, we can independently adjust the number of lasing channels from 2 to 23 at the wavelength spacing of 0.51 nm.     

Temperature-compensating multiple fiber Bragg grating strain sensors with a metrological grating

A novel approach based on multiple fiber Bragg gratings for measuring the distributed strain, which is temperature compensated, is demonstrated. Especially, in order to increase the measurement accuracy, a metrological grating is employed to read out the output of the system. The measurement resolution of the system is less than 0.5 μ.     

Multiple fiber Bragg grating interrogation based on a spectrum-limited Fourier domain mode-locking fiber laser

A novel fiber Bragg grating (FBG) sensing system based on a spectrum-limited Fourier domain mode-locking (SL-FDML) fiber laser is proposed. Multiple FBGs cascaded in a long fiber are utilized as both the sensors in the system and the wavelength-selected components in the SL-FDML fiber laser. Both wavelength-division multiplexing and spatial-division multiplexing techniques are demonstrated for interrogation of multiple FBGs by mapping the wavelength measurement to the time measurement and by adjusting the driving frequency of the SL-FDML fiber laser. The proposed FBG sensing system, employing techniques of the wavelength- and spatial-domain interrogation of multiple FBGs, can be used in remote and quasi-distributed multipoint sensing.     

A novel dual-wavelength fiber Bragg grating and its application in fiber ring laser

A novel method for fabricating dual-wavelength fiber Bragg gratings (FBGs) by using one phase mask is developed. The method is based on a double-exposure technique. Our technique lends itself to writing gratings with controllable reflectivity and separation of two Bragg wavelengths. A grating with two equal transmission peaks of 20.25 dB is obtained by this method and the separation of the two Bragg wavelengths is about 0.8 nm. With the grating, we demonstrate a dual-wavelength erbium-doped fiber ring laser whose interval of the two peaks is 0.8 nm. The laser's peak powers can get 3.1 mW above and have a good stability.     

A novel dual-wavelength fiber Bragg grating and its application in fiber ring laser

A novel method for fabricating dual-wavelength fiber Bragg gratings (FBGs) by using one phase mask is developed. The method is based on a double-exposure technique. Our technique lends itself to writing gratings with controllable reflectivity and separation of two Bragg wavelengths. A grating with two equal transmission peaks of 20.25 dB is obtained by this method and the separation of the two Bragg wavelengths is about 0.8 nm. With the grating, we demonstrate a dual-wavelength erbium-doped fiber ring laser whose interval of the two peaks is 0.8 nm. The laser's peak powers can get 3.1 mW above and have a good stability.     

Eight-wavelength switchable fiber ring laser with ultranarrow wavelength spacing using a quadruple-transmission-band polarization maintaining fiber Bragg grating

We propose and demonstrate an eight-wavelength switchable laser with approximately 40 pm wavelength spacing using a polarization maintaining fiber Bragg grating (PMFBG). This PMFBG has a specially designed quadruple-transmission-band. When it is used in a fiber ring configuration, four wavelengths can be switched in one state of polarization, while the other four can oscillate in the corresponding orthogonal state. PACS 42.55.Wd; 42.81.-i; 42.81.Gs     

Stable single frequency Er-doped all-fiber ring laser with fiber Bragg grating Fabry-Perot filter

Using a fiber Bragg grating (FBG) and a Fabry-Perot cavity composed of two fiber Bragg gratings (FBGFP) as its frequency-selective components, a type of single frequency all-fiber ring laser permits oscillation only on one longitudinal mode of the main cavity without modehopping while the cavity length can be up to tens of meters. The salient feature is due to the single narrowband resonance of the FBGFP filter. Such a fiber ring laser is achieved experimentally, and the laser mode is limited inside the single resonance of the FBGFP.     

Channel spacing-tunable sampled fiber Bragg grating by linear chirp and its application to multiwavelength fiber laser

We theoretically investigated the two methods for densifying the channel spacing of sampled fiber Bragg gratings (SFBGs), the multiple-phase-shift (MPS) method and the linear chirp method, and found that the two methods have similar principle and ability, although the chirp method has an advantage that the tuning of channel spacing is easier. Then we realized channel spacing-tunable SFBGs by use of deformation of ring and S-bend structures by 2- and 3-folds. Finally, we applied the chirp method to realize a wavelength spacing-tunable multiwavelength fiber laser.     

Phase-only sampled 45 channel fiber Bragg grating written with a diffraction-compensated phase mask

A novel phase-only sampled 45 channel fiber Bragg grating (channel spacing, 100 GHz) with high interchannel and intrachannel reflection uniformity and precise dispersion matching capability to an 80 km SMF-28 fiber is demonstrated. This grating is fabricated by the side-writing technique, in which phase information of continuous phase-only sampling is completely incorporated into a diffraction-compensated phase mask.     

Multiwavelength Raman fiber lasers with equalized peak power using a sampled chirped fiber Bragg grating

Two novel multiwavelength Raman fiber lasers using a ring cavity and a linear cavity are proposed and demonstrated experimentally. Both laser configurations include a sampled chirped fiber Bragg grating used in the reflection mode. By adjusting the polarization controller (PC) in the cavities, up to ten stable lasing wavelengths with 0.8 nm spacing and equalized peak power are achieved at room temperature. It is observed that the output spectrum depends upon which port of the grating is connected to the cavity. These two fiber ring lasers offer advantages such as, stable room temperature operation, simple structure, low loss, multiwavelength lasing lines with moderate output power. PACS 42.55.Wd; 42.55.Ye; 42.81.-i     

Ultranarrow dual-transmission-band fiber Bragg grating filter and its application in a dual-wavelength single-longitudinal-mode fiber ring laser

A fiber Bragg grating filter with ultranarrow dual-transmission bands implemented using the equivalent phase shift technique is demonstrated. A fiber ring laser that incorporates a dual-transmission-band fiber Bragg grating filter in the ring cavity is implemented. Dual-wavelength single-longitudinal-mode lasing with a wavelength spacing as small as 0.147 nm at room temperature is experimentally demonstrated.     

Erbium-doped fiber ring laser sensor for high temperature measurements based on a regenerated fiber Bragg grating

This article presents an erbium-doped fiber ring laser for high temperature measurement with high accuracy. The proposed laser sensor employs a regenerated fiber Bragg grating (RFBG) as a sensor element. Through thermal treatments, the RFBG with enhanced thermal resistance was obtained. The laser emission optical spectrum presents good performance with a high optical signal-to-noise ratio of 58dB. Experimental results demonstrate a wavelength sensitivity to the temperature is 15.5 pm/ºC with the temperature range from 300ºC to 900ºC, and the correlation coefficient is 0.999. The results prove it is able to provide potential applications in high temperature measurement.     

A self-seeded fiber laser incorporated with a fiber Bragg grating external cavity semiconductor laser

A self-seeded fiber laser incorporated with a fiber Bragg grating external cavity semiconductor laser (FBG-ECL) and a Mach-Zehnder interferometer (MZI) were reported in this paper. The MZI provided a Q-switching with response time in the order of micro-seconds. The FBG-ECL provided narrow pulses as seeds to shorten the Q-switched pulses. Experimentally, pulse width of 0.8 μs was measured, which was one fifth of the pulse width without self-seeding.     

Multiwavelength Brillouin-erbium fiber laser incorporating a fiber Bragg grating filter

In this paper, we demonstrate a multiwavelength Brillouin erbium fiber laser in a Fabry-Perot cavity. The design utilized a bidirectional oscillation provided by a fiber Bragg grating filter and a fiber loop mirror at each end of the laser cavity. A stable operation of 25 Brillouin-Stokes lines was obtained at around a 1559-nm band.     

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.