Room-Temperature Power-Stabilized Narrow-Linewidth Tunable Erbium-Doped Fiber Ring Laser Based on Cascaded Mach-Zehnder Interferometers with Different Free Spectral Range for Strain Sensing

An automatically power-stabilized (with power fluctuation <0.155 dB), narrow-linewidth (0.0171 nm), wavelength-tunable (10.69 nm) erbium-doped fiber laser has been proposed by cascading two fiber Mach-Zehnder interferometers (MZI) without using any temperature controlling device. One of the MZIs (here called the 1st MZI) is composed of two 3 dB couplers to form interference patterns while the other MZI (here termed the 2nd MZI) is constructed with a tapered seven-core fiber (SCF) and based on the principle of supermode interference. For the two MZIs, the free spectral range (FSR), the passband bandwidth and the extinction ratio (ER) at 1560 nm are 0.37 nm, 0.19 nm, 16.6 dB and 13.93 nm, 7.93 nm, 10.1 dB, respectively. Due to the major difference between the two FSR values, the 1st MZI and the 2nd MZI respectively play a role in controlling the laser linewidth and suppressing the homogeneous broadening effect to reach to a satisfactory level of power stability. The 2nd MZI is also used to fine tune the laser wavelength by applying strain to the tapered SCF (TSCF) over the spectral range of 1570.22-1559.33 nm, with an incremental step of 0.37 nm being used. The side-mode suppression ratio (SMSR) of the tunable fiber laser can be up to 45 dB. By appropriately adjusting the polarization controller, dual wavelength lasing can also be achieved. For single wavelength lasing, the 3 dB laser linewidth is 0.0171 nm. The power fluctuation, without a temperature controlling device being used and operating at room temperature, is found to be less than 0.155 dB over 1 hour while the central wavelength drift is less than 0.19 nm

Single-longitudinal mode laser structure based on a very narrow filtering technique

A narrow filtering technique based on the spectral overlapping of two uniform FBGs and applied to obtain a Single Longitudinal Mode (SLM) laser is proposed and demonstrated in this work. The two FBGs are spectrally detuned to reduce their coincident reflection response narrowing the equivalent filter bandwidth. A proof-of-concept linear laser has been built and tested exhibiting SLM operation even with temperature and strain variations.The authors are grateful to the Spanish government project TEC2010-20224-C02, to the Spanish Ministry of Education and Culture, and to the grant AP2009-1403

A dual wavelength erbium doped fibre ring laser employing 3dB coupler and FBGs in preparation for dispersion measurement

Abstract: A simple dual -wavelength c-band laser source with the aid of Fibre Bragg gratings (FBG) with an optical SNR of up to 70dB is demonstrated. The laser includes a 3,2m Erbium doped fibre with 11,38dB/m absorption in a ring resonating cavity with optical couplers. The ring cavity had two FBGs centred at 1555.12nm and 1560.32nm attached by a 3dB coupler. A 1m long sagnac loop with 70:30 coupling was used to stabilise the dual wavelength emission to about 2dB. The multiwavelength and narrow spectral width of 0.183nm and 0.195nm of the laser can be used for dispersion measurement in WDM communication links which consist of more than one wavelength. The laser was characterised for dual output power response and power stability. The paper present a characterisation of an Erbium doped fibre (EDF) ring laser. The laser is cost effective and dynamic in selecting preferred components for optimal performance in terms of power and wavelength stability, wavelength selectivity and narrow spectral width. EDF lasers are commercial available and already showing great promise in terms of the formidability and compatibility with current industrial requirements