Sampled Fiber Gratings Research Articles

Eight-wavelength EDF laser combining tilted fiber grating with sampled fiber grating

A new eight-wavelength erbium-doped fiber laser, which utilizes linear cavity structure, was designed and experimentally authenticated. The laser was composed of two Sagnac loops: a left loop containing a fiber coupler (FC) with power ratio of 50:50 and a tilted fiber grating (TFG), and a right loop consisting of another FC, a sampled fiber grating (SFG) and three-ring-type polarization controller (PC). The TFG had many inhomogeneous peaks with maximum power differences of 3 dB and maximum modulation depths of 16 dB. Two adjacent transmission peaks in the SFG had approximately 0.3 nm spacings and maximum modulation depths of 8 dB. The two loops with TFG and SFG were jointly utilized to motivate multi-wavelength. When the PC was tuned to cause the PHB effect, 21 sorts of diverse lasing lines were achieved. All lasing lines with the OSNRs of more than 20 dB had fewer than 0.21 nm line widths.

Drawing Tower In-Line Fabrication and the Spectrum Analysis of Sampled Fiber Grating

Sampled fiber grating is a special superstructure fiber Bragg grating with a wide range of applications in many fields. In this work, based on drawing tower in-line fabrication system, a new preparation method of the sampled fiber grating is proposed and experimentally demonstrated. Experimental result shows that the obtained sampled fiber gratings possess dense reflection spectra, with a minimum reflection peak interval of only 0.09nm. This method exhibits promising application prospect in the fabrication of the high-quality sampled fiber grating. On the other hand, the spectral characteristics of the sampled fiber grating are analyzed when the sub-grating is affected by the external physical quantities such as, in this paper, strain. Wavelength shift and intensity change in the reflection peak of the spectra indicate that the grating is affected differently by micro strains, due to the different spatial positions along the axis of the sampled fiber grating. This work is aimed at exploring the potential applications of the sampled fiber grating in quasi-distributed micro-area sensing with the millimeter level.

Sampled fiber gratings for picosecond time delay signal processing

Sampled fiber grating for high-resolution time-domain signal processing is investigated. Sampled fiber grating is useful to introduce precise time delays in picosecond (ps) across many wavelength channels. We analyze and simulate for Sinc2 sampled fiber grating, and show that a large number linear sub-ps time delays can be achieved by the grating. We present that Gaussian sampled fiber gratings can be fabricated by inscribing optical fiber by Gaussian laser beam, and can realize short time delays over a number of wavelength channels with a required time delay profile. For a Gaussian sampled fiber grating fabricated, an average time delay step of 4.49 ps with 10% linearity for 8 wavelength channels, and an average delay step of 2.5 ps with 8% linearity if for 4 channels, are realized. A physical model of cascaded equivalent Fabry-Perot cavities together with rectangular truncation of the inscription laser beam for the Gaussian sampled refractive index is suggested, and used to explain the grating spectra. A technique for time delay step tunability of the grating is presented. Some issues are discussed with conclusions given. We demonstrate that the sampled fiber gratings have capability to provide a large number of picosecond time delays with good linearity. This offers a simple technique for ps-high-resolution signal processing in time-domain and THz signal generation.

Sampled fiber grating for WDM signal queuing with picosecond time interval

A new sampled fiber grating scheme is investigated for WDM signal queuing in time domain. The queuing is aimed at achieving very short constant time intervals down to picoseconds (ps) for many wavelength channels by a single fiber device. Theory and modeling predict that a consistence of linear spectral profiles exists between reflectivity or transmission spectrum and time delay spectrum. A sampled fiber grating based on Gaussian beam writing is proposed to offer a large number of wavelength channels and time delays within an approximate linear profile. Results for simulating a Gaussian sampled fiber grating show that the time delay minima of 8 channels within a section of the spectral profile have an average time delay step of 2.83ps and standard deviation of 7.4% from linearity. Fiber gratings were successfully written by Gaussian laser beam in fabrication. A Gaussian sampled fiber grating was measured for time delay spectrum of 4 wavelength channels. An average time delay step of 9.67ps is obtained. Some issues and related analysis and discussion are given. Our preliminary experiment suggests that the sampled fiber grating scheme can achieve ps-time steps for WDM signal queuing such as high-resolution time delay lines.

The Application of Wavelet Denoise in Sampled Grating Comb Filter

This paper based on the theoretical basis of sampled fiber grating, using transfer matrix method to analyze sampled fiber grating. By changing the parameters of sampled fiber grating and simulating its reflective spectrum. Four optical comb filters based on sampled grating were designed. Then the wavelet de-noising principle was introduced. In order to optimize designing of sampling grating comb filter, a filtering analysis and denoising method by using wavelet analysis to denoise was proposed. Finally, the automatic one-dimensional denoising was used with db6 wavelet. It not only denoise reflective spectrum noise, but also play a certain inhibition in the side-lobe interference the signal received. The smooth reflective spectrum can be got after denoising.

Design of Sampled Fiber Bragg Grating Comb Filter

This article based on the theoretical basis of sampled fiber grating, using transfer matrix method to analyse sampled fiber grating, and the analysed the spectrum of sampled fiber grating, and studied sampled fiber grating filter properties. by adjusting the parameters of sampling grating such as: the length of the grating, grating period, duty ratio ( sampling rate) and other parameters, to construct 6 comb filter, and finally come to sampled fiber grating filter preparation method and process in the theory, analysed the application of sampled fiber grating filter in some optical fiber communication fields.

Sensing Characteristics of Sampled Fiber Bragg Grating about Temperature and Strain

Sampled fiber grating is a novel fiber Bragg grating. Because of it is flexible, passive, low insertion loss and small polarization dependent. It causes great interest and enthusiasm of the people in many areas. Ambient temperature and strain can both affect sampled grating reflection spectrum. On the base of analysis of sampled grating temperature and strain sensing model ,we can use computer to simulate the sampled grating temperature and strain sensing experiments to get Sampled grating temperature sensing data and strain sensing data. By analyzing the factors of temperature and strain which affect the spectral characteristics of the sampled grating, and using regression analysis methods to respectively get the 4 parameters A, B, C, D of sensing properties, so we can simultaneously measure the changes of temperature and strain through single sampled grating.

Output characteristics of wavelength tunable fiber lasers based on sampled Bragg gratings

A simulation model of the fiber DBR (distributed Bragg reflector) laser with two sampled Bragg gratings (SBGs) as reflectors is established, with which the characteristics of the laser are analyzed in detail. The analysis mainly focuses on the change of the laser output characteristics with the wavelength and reflectivity of the front and back sampled fiber gratings. Because of the multi-channel reflection of SBGs, the side mode of such laser is always very obvious. The method for improving the SMSR(side mode suppression ratio) is suggested. And the wavelength tuning mechanism is also studied. Experiment has been carried out to confirm the analysis.

Nonlinear Effects in Widely Tunable ECSL With Sampled Fiber Grating

A theoretical study of nonlinear effects in the external cavity semiconductor laser (ECSL) with sampled fiber grating is presented; such effects are responsible for asymmetric side-mode suppression ratio or power characteristics, and hysteresis phenomena. Impacts of material and geometrical parameters on nonlinear effects of such lasers were analyzed and discussed. Apodization and interleaved technologies were demonstrated to be helpful with expanding tuning range and suppressing nonlinear effects. Based on this, a new ECSL with interleaved sampled grating has been proposed.

A novel method for fabricating sampled fiber grating amplitude mask

A novel method for fabricating sampled amplitude mask is presented, the featureof which is the varying sampling period and fixed sampling duty ratio. By usingsuch an amplitude mask, sampled fiber gratings with different wavelength spacings of reflectivity peaks can be easily fabricated. So the novel method has the advantages of reduced fabrication cost and improved versatility of sampled grating. The possible disadvantages of the method are also discussed. Wavelength selectable fiber laser with vernier wavelength tuning mechanism is also demonstrated by the sampled fiber grating.

Multi-wavelength dispersion compensator based on fiber gratings with low crosstalk

A novel method is proposed to suppress the crosstalk of the DWDM system with dispersion compensated by fiber gratings, combining the merits of both concatenated narrowband fiber gratings and sampled fiber gratings. Random time delay is induced only between the adjacent channels to improve the characteristics of fiber gratings' linear crosstalk, with the cross modulation effects and the four wave mixing effects being suppressed simultaneously. Using this method，we can realize the low crosstalk multi-wavelength dispersion compensators based on fiber gratings.

Tuning of Channel Spacing in Sampled Fiber Gratings by Heat-Induced Multiple-Phase-Shift Technique

We developed a spacing-tunable comb filter using a sampled fiber Bragg grating (SFBG) by heat-induced multiple phase shifting (MPS). We successfully demonstrated two- and three-fold densifications of channel spacing in an experiment.

Pressure mapping sensor with an array of chirped sampled fiber gratings

In this paper, we report the development of a pressure mapping sensor using a chirped sampled fiber grating. The grating is embedded in fiber-reinforced composite. The magnitude of the pressure can be determined from the wavelength shift. The location of the pressure can be determined from the wavelength of the affected sub-grating. The concept has been extended to a two-dimensional array of chirped sampled grating with twenty sensing points in a 1 cm × 6 cm map. The array also gives the pressure and position information when the loading point is not directly on any grating or sub-grating.

Investigation of the output characteristics of multi‐wavelength lasers based on SOAs and sampled fiber gratings

AbstractA novel scheme for multiwavelength lasers, based on semiconductor optical amplifiers (SOAs) and cascaded two‐sectional sampled fiber gratings (SFGs), is analyzed theoretically and experimentally. Reflection spectra for sampled fiber gratings and lasing output spectra for multiwavelength lasers are calculated based on a corresponding theoretical model. By exploiting SOAs and sampled fiber gratings, a multiwavelength laser with 11 channels is specially designed, and an output‐power difference of less than 1 dB is demonstrated. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 142–146, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11308

Improving the performance of fiber gratings with sinusoidal chirps.

Sinusoidal chirps are introduced in fiber gratings to improve their performance as dispersion compensators and multichannel filters. The sinusoidally chirped fiber gratings exhibit a flattop spectrum with steep edges and high reflectivity. The bandwidth utilization defined as the ratio of -1:-30-dB bandwidth could be very high (>0.85). This structure can be applied to the sampled fiber gratings to enhance channel uniformity. We demonstrate 264 uniform channels with a 25-GHz-spacing for high-density-wavelength multiplexing applications. Multichannel dispersion compensations with seven uniform channels of 50-GHz-spacing in short fiber gratings are also demonstrated. The impact of possible fabrication errors on the spectra of the gratings is discussed.

Channel-selectable multichannel optical add/drop multiplexer based on a sampled fiber grating

In this paper, we propose and demonstrate a novel channel-selectable multichannel optical add/drop multiplexer consisting of a sampled fiber grating and tunable fiber Bra99 gratings. The device adds and drops not only single channel, but also any predetermined multiple channels simultaneously with low interchannel crosstalk by wavelength tuning as small as 0.5 nm or less. The interchannel crosstalk better than 27㏈ has been shown experimentally.

Multiwavelength lasers based on semiconductor optical amplifiers

Stable multiwavelength lasing is demonstrated with a novel laser, in which a semiconductor optical amplifier offers optical gain and cascaded sampled fiber gratings serve as a comb filter. Five lasing lines are obtained with a fixed wavelength spacing of 0.8 nm. Optical power fluctuations among the lasing lines are improved by adjusting the reflectivity profile through the cascade of two sampled gratings.