Sagnac Loop Reflectors Research Articles

Stable and uniform multiwavelength erbium-doped fiber laser based on a microfiber knot resonator with a Sagnac loop reflector

In this paper, we proposed and demonstrated a stable and uniform multiwavelength erbium-doped fiber laser (EDFL) by using of the filer action of microfiber knot resonator (MKR) with a Sagnac loop reflector. By embedding the resonator to the ring cavity of the EDFL by means of a circulator, a multiwavelength EDFL is created. The number of the lasing lines with different wavelengths within 3-dB bandwidth is up to 42, the linewidth of each lasing line is about 0.05 nm and the side-mode suppression ratio is about 45 dB. The results demonstrate that the MKR with a Sagnac loop reflector can be employed as a high performance comb filter to realize a stable and uniform multiwavelength fiber laser.

Enhanced slow light in microfiber double-knot resonator with a Sagnac loop reflector

We propose a theoretical model to describe the light-propagation property of the microfiber double-knot resonator with a Sagnac loop reflector. The mathematical relationships between the reflection light field and the input one of this structure are deduced. Numerical simulations indicate that, comparing with the group time delay in the microfiber double-knot resonator, the one in the same resonator but with a Sagnac loop reflector can be enhanced considerably. For comparison, microfiber double-knot resonators with and without a Sagnac loop reflector are both fabricated. Corresponding comparison experiments are performed, which indeed demonstrates the theoretical prediction. A group time delay of about 61ps is achieved experimentally in the resonator with a Sagnac loop reflector, while in the same resonator but without a Sagnac loop reflector it is only about 30ps.

Reflective arrayed waveguide gratings based on Sagnac loop reflectors with custom spectral response.

In this paper, a model for the analysis and design of a reflective Arrayed Waveguide Grating is presented. The device consists of one half of a regular AWG where each arm waveguide in the array is terminated with a phase shifter and a Sagnac loop reflector. By individually adjusting the phase shifter and Sagnac reflectivity in each arm, additional functionality to that previously reported in the literature is attained, since this enables tailoring the spectral response of the AWG. The design and experimental demonstration of Gaussian pass-band shape devices in Silicon-on-Insulator technology are reported. Methods to obtain flattened and arbitrary spectral responses are described and supported by simulation results.

Continuously tunable reflective-type optical delay lines using microring resonators

We present a reflective-type optical delay line using waveguide side-coupled 13 microring resonators terminated with a sagnac loop reflector. Light passes through the microring resonator sequence twice, doubling the delay-bandwidth product. Group delay is tuned by p-i-p type microheaters integrated directly in the microring waveguides. Experiment demonstrates that the delay line can potentially buffer 18 bits and the delay can be continuously tuned for 100 ps with a power tuning efficiency of 0.34 ps/mW. Eye diagrams of a 20-Gbps PRBS signal after 10 and 110 ps delays are also examined.

Integrated Microfibre Device for Refractive Index and Temperature Sensing

A microfibre device integrating a microfibre knot resonator in a Sagnac loop reflector is proposed for refractive index and temperature sensing. The reflective configuration of this optical structure offers the advantages of simple fabrication and ease of sensing. To achieve a balance between responsiveness and robustness, the entire microfibre structure is embedded in low index Teflon, except for the 0.5–2 mm diameter microfibre knot resonator sensing region. The proposed sensor has exhibited a linear spectral response with temperature and refractive index. A small change in free spectral range is observed when the microfibre device experiences a large refractive index change in the surrounding medium. The change is found to be in agreement with calculated results based on dispersion relationships.

Sagnac loop reflector and arrayed waveguide grating-based multi-wavelength laser monolithically integrated on InP

In this study, a multi-wavelength laser monolithically integrated on InP is presented. A linear laser cavity is built between two integrated Sagnac loop reflectors (SLRs), with an arrayed waveguide grating (AWG) as frequency-selective device, and semiconductor optical amplifiers as gain sections. The power is out coupled from the cavity using a side diffraction order of the AWG. Simultaneous laser operation is provided for four wavelengths/cavities in the device. The termination of the laser cavities with integrated SLRs avoids using high-reflection coating. Only anti-reflection coating is used in the output facet of the chip.

Enhanced fast light in microfiber ring resonator with a Sagnac loop reflector

We fabricate a microfiber knot-type ring resonator with a Sagnac loop reflector, and control the light velocity using the device. In this structure, light is reflected by the Sagnac loop and passes through the ring resonator twice. Thus, it possesses doubled transmission and group delay comparing with the microfiber ring resonator without the Sagnac loop. We experimentally demonstrate pulse advancement in an under-coupled microfiber knot-type ring resonator with a Sagnac loop reflector. In the experiment, a maximum of approximately 25 ps pulse advancement was achieved for a 5-Gb/s RZ signal.

Cost-effective tunable fiber laser based on self-seeded Fabry-Perot laser diode using a Sagnac loop reflector

We propose and demonstrate a simple configuration of wavelength-tunable fiber laser made up of a tunable band-pass filter, a Sagnac loop reflector, and a Fabry-Perot laser diode. Based on the self-seeded operation, the proposed fiber laser can obtain a single-longitudinal-mode output in the wavelength tuning range of 1544.69-1563.39 nm with tuning step of 1.34 nm. The performances of output power (>-9 dBm), optical side-mode suppression ratio (> 65.5 dB), and power and wavelength stabilities are well exhibited.

Tunable and injection‐switchable erbium‐doped fiber laser of line structure

AbstractA tunable and injection‐switchable erbium‐doped fiber (EDF) laser is proposed based on a line structure formed by a fiber Sagnac loop reflector and an fiber Bragg grating (FBG). Wavelength switching is achieved by controlling the power of the tunable injection laser. The self‐seeded wavelength corresponding to the Bragg wavelength of the FBG can be tuned by, for example, heating the FBG, and the injection wavelength can be tuned over a wide range of about 50 nm. The characteristics of the wavelength switching for different levels of the EDF pump power and different wavelengths of the injection laser are studied experimentally. The present fiber laser has the advantages of tunability, stability, low amplified spontaneous emission noise, and high injection efficiency when compared with a fiber ring laser. Rapid wavelength switching is expected and the transient switching response of the laser is also studied. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 765–768, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22262

Wavelength Switching of a Fiber Laser With a Sagnac Loop Reflector

A multiwavelength fiber laser is constructed with an elliptical core erbium-doped fiber serving as an anisotropic gain medium. A broadband fiber reflector and a Sagnac loop reflector form a Fabry-Perot resonant cavity. Three lasing wavelengths are obtained which are stable over an hour at room temperatures. With one of them as reference wavelength, we can switch the other two by a polarization controller. The lasing wavelengths are also tunable. The effects of the anisotropic gain behavior of the erbium-doped fiber are also explored.

Sagnac loop reflector and its multiwavelength laser application

A fiber laser is constructed with an erbium-doped fiber, which has an elliptical core and is single-moded along the minor axis and multimoded along the major axis. The laser can emit simultaneously several stable lines at room temperatures. The maximum number of lasing lines obtained depends on the number of modes supported by the erbium-doped fiber in the cavity. The separation between the lasing lines depends on the fiber birefringence. The stability of the lasing lines in the presence of anisotropic gain effects in a polarization-maintaining fiber is explored.

Loss modulation effect on the second-harmonically mode-locked erbium-doped fiber laser based on sagnac loop reflector with y-branch LiNbO/sub 3/ phase modulator

We investigated the loss modulation effect on the second-harmonically mode-locked erbium-doped fiber laser based on the Sagnac loop reflector with a Y-branch LiNbO/sub 3/ phase modulator. We found that even a small loss modulation originating from the phase modulator could cause severe peak power difference between two output pulses in a modulation period. It was also found that the peak power difference was sensitively dependent on the modulation frequency. By numerical simulation, we quantitatively analyzed the relation between the peak power difference and the amount of loss modulation, which agreed well with the experimental results.

Additive-pulse modelocking in fiber lasers

A self-starting additive-pulse modelocked (APM) all-fiber ring cavity laser operating in the negative group velocity regime is analyzed. The advantages of using a ring cavity with an isolator are discussed. The "figure eight" and the Sagnac loop reflector fiber laser are investigated in a novel way, and one form of their operation is related to the master equation of APM. We point out that the ring laser has an advantage with respect to self-starting.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>