Loop Mirror Filter Research Articles

Single-frequency fiber laser at 1627 nm based on a self-designed Er-doped hybridized glass fiber.

Aiming at applications like expanding usable wave band of optical telecommunication and preparing Sr optical lattice clocks, a 1627 nm single-frequency fiber laser (SFFL) is demonstrated based on a 7-m-long self-designed Er-doped hybridized glass fiber (EDHF) and a linear cavity configuration with a loop mirror filter (LMF). By inserting a 10-m-long unpumped commercial Er-doped fiber as a dynamic Bragg grating into the LMF, a stable single-longitudinal-mode (SLM) laser with an output power of about 10 mW is obtained. The optical signal-to-noise ratio (OSNR) of SFFL is over 50 dB, and the linewidth is about 3.7 kHz. The measured relative intensity noise (RIN) is less than -140 dB/Hz at frequencies of over 0.5 MHz, and a power variation in 1 h is less than ±0.26%. To our best knowledge, it is the first demonstration of a SFFL operating at the U-band. This 1627 nm SFFL can provide advanced light source technology support for many cutting-edge applications.

Q-switched tunable fiber laser with aluminum oxide saturable absorber and Sagnac loop mirror

A Q-switched erbium-doped fiber laser with tunable output wavelength was demonstrated by utilizing aluminum oxide saturable absorber in conjunction with Sagnac loop mirror (SLM) filter. As the SLM temperature was increased from 30 to 70 °C, the laser operation can be tuned from 1568 to 1556 nm. At 1568 nm operation, the laser pulse frequency can be raised from 13.66 to 26.25 kHz by increasing the pump power from the threshold of 53 to 87 mW. With the increase in temperature, it is found that the pump threshold for the Q-switching increased, while the laser operation shifted to a shorter wavelength.

Q-switched and tunable wavelength fiber laser utilizing nickel oxide saturable absorber and sagnac loop mirror filter

We demonstrate a Q-switched Erbium-doped fiber laser (EDFL) with a tunable output wavelength using Nickel oxide (NiO) saturable absorber (SA) in conjunction with a Sagnac loop mirror (SLM) filter. The proposed SA was prepared by embedding NiO nanoparticles obtained bysimplistic sonochemical reaction into polyethylene oxide (PEO). The NiO PEO film was integrated into a figure-of-eight resonator configured with a SLM to generate Q-switched pulses with a tunable output wavelength. As the SLM temperature was increased from 30 °C to 70 °C, the laser operation can be tuned from 1551.9 nm to 1544.1 nm. At 1551.9 nm operation, the repetition rate rose from 36.2 kHz to 40.3 kHz and the pulse duration reduced from 10.00 to 9.32 μs when the pump power rose from 131.5 to 161.0 mW. At the highest pump power of 161.0 mW, the maximum output power and pulse energy were obtained at 0.67 mW and 16.6 nJ. For Q-switched operation at 1544.1 nm, the produced Q-switched pulse exhibited a pulse duration of 8.88 μs, the repetition rate of 45.7 kHz, the highest output power of 0.60 mW and pulse energy of 13.1 nJ at the maximum pump power of 161.0 mW.

Tunable and Switchable Multi-wavelength Erbium-Brillouin Random Fiber Laser Incorporating a Highly Nonlinear Fiber

A tunable and switchable multi-wavelength Erbium–Brillouin random fiber laser (MW-EBRFL) with a half-open cavity structure and incorporating a segment of highly nonlinear fiber (HNLF) is proposed and experimentally demonstrated. Due to HNLF being with high nonlinear coefficient, high Brillouin gain coefficient and high Rayleigh scattering (RS) coefficient, a reduced length of HNLF can provide a strong random distributed feedback (RDFB) and high stimulated Brillouin scattering (SBS) gain. In addition, an optical fiber amplify loop (OFAL) including a high-power erbium-doped fiber amplifier (HP-EDFA) and an optical attenuator (ATT) is constructed to provide a strong Brillouin pump (BP) and controllable optical feedback. Using the presented MW-EBRFL, up to 11 orders of stable Stokes laser lines with a wavelength spacing of 0.074 nm and the minimum optical signal-to-noise ratio (OSNR) of 41.22 dB are obtained. System parameters including BP power and HP-EDFA pump power influence on output of MW-EBRFL are also investigated. By adjusting BP wavelength, multi-wavelength output with 6–11 channel numbers can be tuned in a wide wavelength range spanning 36 nm. The proposed MW-EBRFL also can realize switchable multi-wavelength generation of 1 ∼ 11 order Stokes with an increasing wavelength number in turn, only by simply adjusting HP-EDFA pump power. Furthermore, when a polarization-maintaining fiber loop mirror filter (PMF-LMF) is cascaded with output port of the cavity, it can be very convenient to achieve wavelength switching between single- and double-Brillouin frequency spacing (BFS), only by tuning polarization controller in PMF-LMF.

High-Stability Broadband Wavelength-Tunable Single-Frequency Ytterbium-Doped All-Fiber Compound Ring Cavity

A high-stability wavelength-tunable single-frequency (SF) ytterbium-doped all-fiber compound ring laser has been demonstrated experimentally. The compound ring cavity is composed of a fiber optical tunable filter, a high-finesse ring filter, and a loop mirror filter. Three segments of ytterbium-doped fibers are employed as the gain medium or saturable absorber, respectively. The SF operation is observed to be stable during 1 h without mode hopping. The SF fiber laser achieves a wide-band tunability from 1030 to 1090 nm with maximum output slope efficiency of 7.95%. The power instability over 2 h gives standard deviation value of 1.34%. The average linewidth is 8.8 kHz and the relaxation oscillation frequency is at 62 kHz.

Tunable second-order, birefringent interferometric filter for dynamic chirp management

A tunable second-order birefringent interferometric filter for minimizing signal degradation due to chirping in modulated lasers is proposed and demonstrated. Compared with commonly used filters with standard Gaussian and super-Gaussian filter profiles, a high-order loop mirror filter of similar bandwidth has a much sharper filtering slope. This provides more effective, specific filtering of desired components of a signal’s spectrum, minimizing signal power loss experienced during filtering. The steep filtering slope also provides significant improvement in transmission performance even with a change in data rate. Thus, the same filter can be reused for different bit rates. Furthermore, the tuning capability of the loop mirror filter enables good transmission performance when a variation in signal wavelength is present. Moreover, the unique, periodic filter profile potentially enables chirp management for multiple channels at different wavelengths. We experimentally verify the chirp management performance of the second-order birefringent loop mirror filter. Improvements to the transmission performance of both directly modulated lasers and electro-absorption modulated lasers at different data rates are achieved.

Wavelength-Tunable Single Frequency Ytterbium-Doped Fiber Laser with Loop Mirror Filter**Supported by the International Cooperation Projects of Ministry of Science and Technology under Grant No 2012DFB10120, and the National Natural Science Foundation of China under Grant No 61177059.

By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4nm intervals range from 1063.3 to 1065.7nm with the temperature change of the fiber Bragg grating. The maximum output power could reach 32mW while the pump power increases to 120mW. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.

Tunable multiwavelength erbium-doped fiber laser based on nonlinear optical loop mirror and birefringence fiber filter

A tunable multiwavelength erbium-doped fiber laser (MWEDFL) based on nonlinear optical loop mirror (NOLM) and tunable birefringence fiber filter (BFF) is proposed and demonstrated. By combination of intensity-dependent loss modulation induced by NOLM and pump power adjustment, the proposed laser can achieve independent control over the number of lasing lines, without affecting other important characteristics such as channel spacing and peak location. In addition, the laser allows wavelength tuning with both the peak location and the spectral range of lasing lines controllable. Specifically, the peak location of lasing lines can be controlled to scan the whole spectral range between adjacent channels of comb filter by adjusting the BFF. Moreover, the spectral range of lasing lines can be controlled by adjusting NOLM. This tunable MWEDFL may be useful for fiber-optic communication and fiber-optic sensing.

Quantum dot SOA/silicon external cavity multi-wavelength laser.

We report a hybrid integrated external cavity, multi-wavelength laser for high-capacity data transmission operating near 1310 nm. This is the first demonstration of a single cavity multi-wavelength laser in silicon to our knowledge. The device consists of a quantum dot reflective semiconductor optical amplifier and a silicon-on-insulator chip with a Sagnac loop mirror and microring wavelength filter. We show four major lasing peaks from a single cavity with less than 3 dB power non-uniformity and demonstrate error-free 4 × 10 Gb/s data transmission.

Single frequency Yb-doped fiber laser based on graphene loop mirror filter

We report a new method for obtaining a stable single-frequency Yb-doped fiber laser by introducing a graphene film into a fiber loop mirror combined with a simple linear cavity. The graphene film acts as a saturable absorber so as to form a dynamic absorbing grating in the 3 dB fiber loop. This grating is like a narrow-band filter for discriminating and selecting longitudinal modes. Moreover, we use a polarization controller in the linear resonator to suppress the spatial hole burning effect. The maximum output power is 16 mW at 1 064 nm with a pump power of 110 mW at 975 nm, the slope efficiency is 15%, and the SNR is about 60 dB. To the best of our knowledge, this is the first demonstration of a 1 064 nm single-frequency laser based on a linear cavity with a graphene-loop mirror filter.

A novel double-Brillouin-frequency spaced multi-wavelength Brillouin erbium-doped fiber laser based on non-linear amplified fiber loop mirror

In the paper, a ring double-Brillouin-frequency spaced multi-wavelength Brillouin erbium-doped fiber laser based on non-linear amplified fiber loop mirror filter is demonstrated, in which the non-linear amplified fiber loop mirror (AFLMF) is used as a filter. At the 980nm pump power of 10.29dBm, the tunable laser source center wavelength of 1563nm and power of −3dBm, up to 12 even output channels with 0.16nm spacing are achieved. At the same time, we study the influence of 980nm pump power, the polarization controller and the tunable laser source center wavelength on the number of Stokes light wave.

High-speed wavelength tunable DPSK demodulation using a phase modulator based loop mirror filter.

A high-speed wavelength tunable differential phase-shift-keying (DPSK) signal demodulator is presented using a phase modulator (PM) based fiber loop mirror filter. By controlling the birefringence of the PM inside the loop through electro-optic effect, wavelength tuning speed of tens of GHz and tuning range of over two free spectral ranges are achieved. Stable filter spectra with extinction ratio over 30dB are obtained through the tuning process. By combining the birefringence of polarization maintaining fiber and PM, error-free demodulation performance is experimentally achieved throughout the wavelength tuning range for DPSK signals with flexible bit-rate range from 2.5 to 10 Gb/s. This design significantly improves the wavelength tuning speed and is potentially valuable for high-speed switching and tuning applications.

A wavelength spacing switchable and TUNABLE high‐birefringence fiber loop mirror filter

ABSTRACTWe demonstrated an all‐fiber birefringent comb filter with tunable and switchable wavelength spacing. The comb filter is based on a fiber loop mirror (FLM) with three sections of high‐birefringence (HB) fibers and polarization controllers (PCs). The transmission characteristics of the birefringent FLM are dependent of the relative phase difference of the two orthogonal polarization modes and the rotational angles of the different HB fibers. By adjusting the PCs, four different wavelength spacings can be obtained; particularly, interleaving operation—halved and quartered wavelength spacing—can be effectively realized. By using a Jones matrix method, the transmission of the birefringent comb filter is analyzed. The theoretical analysis agrees with the experimental results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1666–1670, 2014

Slope efficiency over 30% single-frequency ytterbium-doped fiber laser based on Sagnac loop mirror filter

A high-slope-efficiency single-frequency (SF) ytterbium-doped fiber laser, based on a Sagnac loop mirror filter (LMF), was demonstrated. It combined a simple linear cavity with a Sagnac LMF that acted as a narrow-bandwidth filter to select the longitudinal modes. And we introduced a polarization controller to restrain the spatial hole burning effect in the linear cavity. The system could operate at a stable SF oscillating at 1064nm with the obtained maximum output power of 32mW. The slope efficiency was found to be primarily dependent on the reflectivity of the fiber Bragg grating. The slope efficiency of multi-longitudinal modes was higher than 45%, and the highest slope efficiency of the single longitudinal mode we achieved was 33.8%. The power stability and spectrum stability were <2% and <0.1%, respectively, and the signal-to-noise ratio measured was around 60dB.

Broadly tunable L-band multiwavelength BEFL utilizing nonlinear amplified loop mirror filter

We demonstrate a widely tunable L-band multiwavelength Brillouin-erbium fiber laser utilizing a nonlinear amplified fiber loop mirror filter (AFLMF). By manipulating polarization controllers placed in the fiber loop, the erbium peak gain spectrum is able to be shifted. The nonlinear AFLMF induces wavelength-dependent cavity loss and serves as an amplitude equalizer. In addition, it provides flexibility on controlling the amount of light reflected and transmitted into and out of the laser's cavity. By utilizing 100 mW 1480 nm pump and 1.1 mW Brillouin pump power, an average of 24 stable output channels are generated by the proposed structure that could all be tuned over the whole L-band window from 1570 nm to 1610 nm.

An FBG Strain Sensor Demodulation Technique Using Temperature- Compensation HBF Sagnac LM

A novel method of a fiber Bragg grating (FBG) stain sensor demodulation technique is presented. An experimental system is built up in which high birefringence fiber (HBF) Sagnac loop mirror (LM) is used as the edge filter. In order to improve the temperature stability of the system, we have experimentally demonstrated that packaged HBF can compensate the temperature shit of the HBF Sagnac LM filter. The shift of wavelength for an uncompensated HBF Sagnac LM is approximately 2.3nm/0C, and that of the compensated HBF Sagnac LM is 0.03nm/0C, which is much less than that of the uncompensated HBF Sagnac LM filters. Using the temperature-compensation HBF Sagnac LM, We achieve linear demodulation of FBG strain sensor with a range of about 1900 and the strain sensitivity is about 0.14 w/ .

Simplified photonic microwave frequency measurement using a loop mirror filter

A more simplified photonic microwave frequency measurement configuration based on a loop mirror filter is proposed and experimentally demonstrated. It is implemented by propagating a carrier-suppressed double-sideband modulated optical signal through a loop mirror filter. The ratio between the optical powers of the two output ports provides a direct measurement of the unknown signal frequency. This scheme can solve the main problems that exist in previous work. A proof-of-concept experiment is performed with a measurement range of 6 to 18 GHz and resolution less than 0.35 GHz.

Theory and experiment of a fiber loop mirror filter of two-stage polarization-maintaining fibers and polarization controllers for multiwavelength fiber ring laser

A fiber loop mirror (FLM) filter with two-stage polarization-maintaining fibers (PMFs) and polarization controllers (PCs) is presented. The transmission function of this FLM is calculated in detail by Jones matrix. The wavelength interval depends on both the PMFs and the PCs. The side frequencies can be restrained by choosing appropriate length of the PMFs. Furthermore, an erbium-doped fiber ring laser based on this FLM filter is proposed and demonstrated. Stable single-, double- and triple-wavelength are achieved respectively. The 3 dB line-width is less than 0.03 nm, and the fluctuation of wavelength and peak power is less than 0.05 nm and 0.1 dB in 30 minutes.

All-optical clock recovery of 20 Gbit/s NRZ-DPSK signals using polarization-maintaining fiber loop mirror filter and semiconductor optical amplifier fiber ring laser

All-optical clock recovery (CR) from 20 Gbit/s nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) signals are demonstrated experimentally by using a polarization-maintaining fiber loop mirror filter (PMF-LMF) and a semiconductor optical amplifier (SOA) fiber ring laser. Only by adjusting polarization controller (PC), NRZ-DPSK signals were conveniently and fast converted to pseudo return-to-zero (PRZ) signal via PMF-LMF. Then the PRZ signals are injected into the SOA fiber laser for CR. The recovered clock signals is with the extinction ratio (ER) of 10 dB and the root-mean-square (RMS) timing jitter of 750 fs in 2 31 − 1 long pseudorandom binary sequence (PRBS) NRZ-DPSK signals measurement. Moreover, the broad wavelength tunability of recovered clock stemmed from the use of SOAs as modulator and the gain medium are shown too.

Robust optical signal-to-noise ratio monitoring scheme using a phase-modulator-embedded fiber loop mirror

We propose and experimentally demonstrate a novel in-band optical signal-to-noise ratio (OSNR) monitoring technique using a phase-modulator-embedded fiber loop mirror. This technique measures the in-band OSNR accurately by observing the output power of a fiber loop mirror filter, where the transmittance is adjusted by an embedded phase modulator driven by a low-frequency periodic signal. The measurement errors are less than 0.5 dB for an OSNR between 0 and 40 dB in a 10 Gbit/s non-return-to-zero system. This technique was also shown experimentally to have high robustness against various system impairments and high feasibility to be deployed in practical implementation.