A self-frequency-locked multi-wavelength erbium-doped fibre ring laser

A self-frequency-locked laser in a 1.55 m band is demonstrated by adding a segment of samarium-doped fibre (SDF) into an erbium-doped fibre (EDF) ring laser cavity. The narrow band output signal, with a 3 dB down line width of less than 0.15 nm and a side-mode suppression ratio larger than 30 dB, is nearly polarization independent. A multiwavelength EDF ring laser source, using a 1×n synchronous optical switch and n segments of SDF with different lengths, is proposed.     

Switchable multi-wavelength fiber ring laser using a side-leakage photonic crystal fiber based filter

A switchable multi-wavelength fiber ring laser is proposed and experimentally demonstrated with a novel side-leakage photonic crystal fiber (SLPCF) based filter incorporated into the ring cavity at room temperature. Stable multi-wavelength laser operations can be achieved due to the spatial mode beating, polarization hole burning and spectral hole burning effects. By adjusting the polarization controller appropriately, the laser can be switched among the single-, dual- and triple-wavelength lasing oscillations whose signal-to-noise ratio is up to 50 dB. In addition, the lasing wavelength can be also tuned and switched by applying the strain to the filter.     

Polarimetric fibre laser sensors using Er-doped fibre

A polarimetric fibre laser sensor with narrow polarization mode beat frequency bandwidth is demonstrated using a polarization-maintaining Er-doped fibre. The slope coefficients of 124kHz°C^-1 cm^-1 and 137kHz m^-1 are obtained for temperature change and longitudinal strain measurements, respectively. A new configuration of polarimetric fibre laser sensor is also demonstrated using a conventional Er-doped fibre as a gain medium and a short length of polarization-maintaining fibre as a sensing part.     

Switchable multi-wavelength erbium-doped fiber ring laser based on cascaded polarization maintaining fiber Bragg gratings in a Sagnac loop interferometer

A switchable multi-wavelength erbium-doped fiber (EDF) ring laser based on cascaded polarization maintaining fiber Bragg gratings (PMFBGs) in a Sagnac loop interferometer as the wavelength-selective filter at room temperature is proposed. Due to the polarization hole burning (PHB) enhanced by the PMFBGs, stable single-, dual-, three- and four-wavelength lasing operations can be obtained. The laser can be switched among the stable single-, dual-, three- and four-wavelength lasing operations by adjusting the polarization controllers (PCs). The optical signal-to-noise ratio (OSNR) is over 50 dB.     

Stable SOA-based multi-wavelength fiber ring laser using Sagnac loop mirror incorporating a high-birefringence photonic crystal fiber

Multi-wavelength fiber laser using semiconductor optical amplifier (SOA) and Sagnac loop mirror (SLM) incorporating a newly designed high-birefringence photonic crystal fiber (HB-PCF) is experimentally demonstrated. The modal birefringence of the fabricated HB-PCF is estimated to be 1.1 × 10⁻³. Mainly, by adjusting a polarization controller in the fiber ring laser, the proposed fiber laser can operate at six lasing wavelengths with 2.7 nm intervals, the signal-to-noise ratio (SNR) of around 30 dB. The output power stability is 0.8 dB. In addition, we obtained near-perfect temperature independence in our multi-wavelength fiber laser system. The temperature dependence of the SLM is around 3 pm/°C.     

Electro-optic wavelength-tunable fiber ring laser based on cascaded composite Sagnac loop filters

A continuous wavelength-swept fiber ring laser with a lithium niobate waveguide electro-optic polarization controller in an intracavity fiber Sagnac loop is experimentally demonstrated. Composite fiber Sagnac loop filters are cascaded to demonstrate discrete wavelength switching of a single-wavelength fiber ring laser. Stable single-longitudinal-mode operation is achieved by use of a Sagnac loop saturable-absorber filter.     

Switchable multi-wavelength fiber laser based on modal interference

A comb fiber filter based on modal interference is proposed and demonstrated in this paper. Here two cascaded uptapers are used to excite the cladding mode, and a core-offset jointing point is used to act as an interference component.Experimental results show that this kind of structure possesses a comb filter property in a range of the C-band. The measured extinction ratio is better than 12 dB with an insertion loss of about 11 dB. A switchable multi-wavelength erbium-doped fiber laser based on this novel comb filter is demonstrated. By adjusting the polarization controller, the output laser can be switched among single-, dual-, and three-wavelengths with a side mode suppression ratio of better than 45 dB.     

Switchable multiple lasing oscillations in an erbium-doped fiber ring laser using a single stage of a Sagnac loop mirror

A simple scheme for a switchable multi-wavelength erbium-doped fiber (EDF) ring laser is investigated by using a single stage of a Sagnac loop mirror. The multiple lasing outputs are obtained and switched readily by controlling the state of polarization (SOP). Since the transmission characteristics of the Sagnac loop mirror in terms of peak wavelengths and peak powers strongly depend on the SOP, the switching performance of the proposed multi-wavelength EDF laser can be effectively obtained. The proposed multi-wavelength EDF laser has versatile lasing outputs in states of a single-, dual-, triple-, and quadruple-wavelength oscillations. The multiple outputs are effectively switchable by adjusting the SOP.     

Switchable erbium-doped fiber ring laser based on Sagnac loop mirror incorporating few-mode high birefringence fiber

Without the need of any other additional filtering device, a triple-wavelength switchable erbium-doped fiber ring laser based on Sagnac loop mirror incorporating a piece of few-mode high birefringence fiber is newly proposed and experimentally demonstrated. Three potential lasing wavelengths at about 2.0 nm interval with the side mode suppression ratio higher than 40 dB can be switched mainly by adjusting a polarization controller next to the few-mode high birefringence fiber in the Sagnac loop. In addition to the stable single-line lasing operation, simultaneous dual- and triple-line oscillations are also highly stable at room temperature with suppressing the intrinsic homogeneous gain broadening of the erbium-doped fiber.     

Sagnac干涉仪与光纤环形激光器

依据相干光学理论,以现代激光干涉侧试技术中的光纤Ｓａｇｎａｃ干涉仪为例,分析和讨论了光纤环形激光器的基本工作原理,并结合其物理原理简要介绍了光纤环形激光器和光纤陀螺（ＦＯＧ）的应用的发展前景。     

Switchable multi-wavelength fiber ring laser based on a compact in-fiber Mach-Zehnder interferometer with photonic crystal fiber

Switchable multi-wavelength fiber ring laser with an in-fiber Mach-Zehnder interferometer incorporated into the ring cavity serving as wavelength-selective filter at room temperature is demonstrated. The filter is formed by splicing a section of few-mode photonic crystal fiber (PCF) and two segments of single mode fiber (SMF) with the air-holes on the both sides of PCF intentionally collapsed in the vicinity of the splices. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-, dual- and triple-wavelength lasing operations by exploiting polarization hole burning (PHB) effect.     

A tunable narrow-line-width multi-wavelength Er-doped fiber laser based on a high birefringence fiber ring mirror and an auto-tracking filter

A novel multi-wavelength erbium-doped fiber laser operating in C-band is proposed and successfully demonstrated. The wavelength interval between the wavelengths is about 0.22 nm. The 3 dB bandwidth of the laser is about 0.012 nm, and the output power reaches 4.8 mW. By using a high birefringence fiber ring mirror (HiBi-FLM) and a tunable FBG, the laser realizes switchable and tunable characteristic. The mode hopping can be effectively prevented. Moreover, this laser can improve wavelength stability significantly by taking advantage of an un-pumped Er³⁺-doped fiber at the standing-wave section. The laser can operate in stable narrow-line-width with single-, dual-wavelength, and unstable triple-wavelength output at room temperature.     

Switchable multi-wavelength erbium-doped fiber laser based on a four-mode FBG

We propose a switchable multi-wavelength erbium-doped fiber laser based on a four-mode fiber Bragg grating(FBG). The four-mode FBG is fabricated in a hydrogen pre-loaded fiber by the phase mask method, which can support four linearly polarized modes around 1550 nm. The five operation wavelengths are at 1547.5, 1546.8,1546.0, 1545.1, and 1544.2 nm, respectively. Through adjusting the polarization state and the lateral offset coupling in cavity, the laser can be switched into the operation state of single, dual, or triple wavelengths. The proposed laser has the advantages of simple configuration, stable operation, and easy adjustment.     

Narrow-linewidth single-polarization frequency-modulated Er-doped fiber ring laser

We demonstrate a 1550-nm narrow-linewidth fiber ring laser with stable single polarization by using single-mode Er-doped fiber as active fiber and saturable absorber. A polarization-maintaining circulator is used to acquire single-polarization laser light with the degree of polarization of 99.8%--99.9%. The linewidth measured using a delayed self-heterodyne method is less than 0.5 kHz. Frequency of the fiber laser can be modulated by driving the waveguide phase modulator with proper voltage. A Mach-Zehnder interferometer with the optical path difference between two arms of about 36 km is used to study the long-distance coherent detection of the fiber laser for frequency-modulated continuous-wave application.     

Stable multi-wavelength erbium-doped fiber laser based on dispersion-shifted fiber and Sagnac loop filter

A multi-wavelength erbium-doped fiber laser (MEDFL) with simple line structure is experimentally demonstrated by using a Sagnac interferometer as a comb filter. It is shown that the multi-wavelength lasing is quite stable at room temperature due to the four-wave mixing (FWM) effect among different laser channels in the dispersion-shifted fiber cooperated in the laser cavity.     

Sagnac effect in the colliding-pulse-mode-locked dye ring laser

A colliding-pulse-mode-locked dye ring laser was mounted on a rotary stage and the beat frequency of the two output pulse trains was measured as a function of the rotation rate. The measurements are in good agreement with the Sagnac theory.     

Er-doped fiber ring laser gyroscopes operating in continuous waves

A direction related polarizer was inserted into a ring laser cavity to eliminate one of the two eigen-modes as well as spatial hole burning of the gain medium in a bidirectional Er-doped fiber ring laser. Thus, a fiber ring laser gyroscope (FRLG) operating in continuous wave was demonstrated. A beat signal of over 30-dB noise was observed and a good inear relation between the beat frequency shift and cavity rotation rate was obtained.     

Switchable dual-wavelength passively mode-locked fiber ring laser using SESAM and cascaded fiber Bragg gratings

We propose and demonstrate an efficient and simple wavelength switchable dual-wavelength passively mode-locked fiber ring laser based on a semiconductor saturable absorber mirror (SESAM) and a cascaded sequence of fiber Bragg gratings (FBGs). The efficient self-starting mode-locked operation was realized with a SESAM. Dual-wavelength pulses with a wavelength spacing of 12.49 nm were obtained which was determined by the reflection peaks of the FBGs used in the experiment. In addition, by rotating the polarization controllers (PCs), the switchable dual-wavelength operation was simply achieved via exploiting wavelength-dependent loss mechanism.     

Tunable fiber ring laser employing a Sagnac interferometric filter

A tunable erbium-doped fiber ring laser employing an all-polarization-maintaining fiber loop filter is proposed and demonstrated. The lasing frequencies can be selected by properly adjusting the polarization controller in the cavity.     

Er-doped fibre laser mode-locked by mechanically exfoliated graphene saturable absorber

Erbium-doped fibre laser mode-locked by a graphene saturable absorber is presented. Pulses with 630-fs duration and 41.9-MHz repetition frequency were achieved at the centre wavelength of 1562 nm and 9-nm FWHM bandwidth. Multilayer graphene was obtained by mechanical exfoliation from a pure graphite block by using the scotch-tape method and deposited on a fibre ferrule to form a saturable absorber. The laser operated in a mode-locked regime with 37-mW pumping and 4-mW output power.