Sampled Bragg Gratings Research Articles

Performance analysis of Comb filters based on sampled fiber Bragg gratings

AbstractReflection performances of sampled Bragg gratings are simulated using the piecewise‐uniform method. The identical characteristics of reflection spectrum are emphasized in terms of the linewidth and reflectivity. A perfect comb filter with identical channel linewidth and uniform reflectivity is demonstrated, employing the sinc‐sampled grating. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 84–87, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10681

Apodization compensation of sampled Bragg grating by off-coherent zone second exposure

Numerical results show that only apodization compensation is necessary for apodized binary sampled Bragg grating, while sampling compensation is not necessary. A novel off-coherent zone preconditioning approach is proposed which does not require to remove the phase mask. Experiments demonstrate the apparent improvements in the quality of reflectivity and group delay spectrum.

Design optimization of chirped sampled Bragg grating for dispersion compensation

Analytical expressions for the output pulse broadening and eye-diagram power penalty of a chirped sampled Bragg grating (CSBG) dispersion compensator are derived. The result is applied to optimize the design of residue dispersion ratio in each channel and the total channel number of a fixed-length CSBG. The optimal residue dispersion ratio does not change when the channel number changes. The filter-induced pulse distortion will induce an additional eye-diagram power penalty and will give an upper limit for the channel number of 40-G+ systems. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 171–174, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10267

Design optimization of chirped sampled Bragg grating for dispersion compensation

AbstractAnalytical expressions for the output pulse broadening and eye‐diagram power penalty of a chirped sampled Bragg grating (CSBG) dispersion compensator are derived. The result is applied to optimize the design of residue dispersion ratio in each channel and the total channel number of a fixed‐length CSBG. The optimal residue dispersion ratio does not change when the channel number changes. The filter‐induced pulse distortion will induce an additional eye‐diagram power penalty and will give an upper limit for the channel number of 40‐G+ systems. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 171–174, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10267

A novel method to achieve various equivalent chirp profiles in sampled Bragg gratings using uniform-period phase masks

Properly designed sampling function of a sampled Bragg grating can produce an equivalent chirp profile within reflection bands with non-zero Fourier orders. This method has the advantage that various equivalent chirp profiles can be achieved while the phase mask used in the fabrication process needs not to have any chirp. The principle of this method is demonstrated by the fabrication of a sampled fiber Bragg grating with a linear equivalent chirp profile using a uniform-period phase mask.

A novel adjustable PMD compensation using sampled Bragg gratings with uniform grating period

We propose a novel solution for linearly tunable polarization mode dispersion (PMD) compensation by sampled Bragg gratings fabricated with uniform-period phase masks. This all-fiber PMD compensation technique is cost-effective and flexible in designing the differential group delay (DGD) profile. Based on numerical simulations, the efficiency of this PMD compensator is assessed for the 10 Gb/s NRZ transmission system with large DGD. With this compensator, a significant improvement can be achieved in the eye pattern of the received signal.

A novel simple measurement technique of equivalent chirp in the grating period of sampled Bragg grating

In this letter, based on the proposed concept of Moiré sampled Bragg grating (SBG), the equivalent chirp rates of various Fourier orders in a sampled Bragg grating with chirp in the sampling period (CSP) is demonstrated for the first time via a simple novel experimental method using phase mask rotation and dual exposure technique. Difference between experimental data and calculated results is less than 9%.

Correction to "Analytical expression of sampled Bragg gratings with chirp in the sampling period and its application on dispersion management design in a WDM system"

The presented equation leads to a refractive index modulation which is used in the subsequent derivations and calculations. We give a correction to this analytical expression.

Experimental investigation of a sampled grating with a chirp in the sampling period

AbstractIn this letter, a sampled Bragg grating (SBG) with a chirp in the sampling period (CSP) is fabricated and experimentally investigated for the first time. Its spectrum response shows that the effective chirp in the grating period (CGP) varies among stopbands, which is consistent with the previous theoretical predictions. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 128–130, 2001.

Experimental Investigations of a Stress-Gradient Sampled Bragg Grating with a Chirp in the Sampling Period

The spectrum response of a sampled Bragg grating (SBG) with a chirp in the sampling period (CSP) under stress-gradient is experimentally investigated for the first time. It is shown that unlike in a conventional SBG without CSP, the bandwidths of the multiple stopbands vary with the stress asymmetrically around the center Bragg wavelength. These results coincide with the theoretical predictions presented by us. The present experimental demonstration is useful for the application of the SBG with CSP in dispersion slope compensation of fiber in dense wavelength division multiplexing (DWDM) systems.

Periodical corrugated structure for forming sampled fiber Bragg grating and long-period fiber grating with tunable coupling strength

A novel corrugated structure on an optical fiber is proposed and demonstrated to produce tunable long-period index modulation based on photoelastic effect. The corrugated structure is a periodic variation made by chemical etching on the cladding radius of an optical fiber. By imposing this corrugated structure upon a built-in fiber Bragg grating (FBG), a superstructure grating with tunable reflectance is formed. In addition, couplings between the fundamental core mode and cladding modes take place under such a corrugated structure when the phase-matching condition is satisfied. Thus, the device can also act effectively as a long-period fiber grating (LPFG) with tunable coupling strength. We also develop the coupled-mode theory based on Fourier series expansion to describe such a corrugated sampled Bragg grating. The phase-matching condition for various sampling orders can be derived, and the calculated spectra are compared with those based on the fundamental matrix method. Optical measurements demonstrate some unique characteristics of these devices, and good qualitative agreements between simulation and measurement verify the viewpoint that long periodic index modulation is indeed induced by such a corrugated structure through the photoelastic effect when a tensile force is applied.

Numerical investigation of a stress-gradient sampled Bragg grating for dispersion compensation applications in wavelength-division multiplexing systems

In this paper, stress-gradient sampled Bragg grating (SBG) has been studied for the first time. The stress gradient can produce both chirps in the grating period and the sampling period. The group delay of the stress-gradient SBG is different from that of the normal chirped SBG. Based on direct calculations, it shows that stress-gradient chirped SBG can compensate for fiber dispersion and dispersion slope simultaneously in wavelength-division multiplexing systems.

Analytical expression of sampled Bragg gratings with chirp in the sampling period and its application in dispersion management design in a WDM system

Analytical expression of sampled Bragg gratings with chirp in the sampling period and its application in dispersion management design in a WDM system

Strong sampled Bragg gratings for WDM applications

Strong sampled Bragg gratings are UV induced in planar low-loss silica waveguides. Using such gratings, multichannel wavelength-division-multiplexing (WDM) components can be manufactured with high precision. An ASE filter and multichannel add/drop multiplexer have been demonstrated and characterized using sampled gratings and optical circulators. The add/drop multiplexer exhibits an intraband crosstalk of -30 dB and an interband crosstalk of -20 dB when used with a 200-GHz channel spacing. Simulations using a matrix method are performed showing that the use of uniform sampled gratings is limited by interband crosstalk to channel spacings of around 100 GHz. Propagation losses induced by the amplitude modulated superstructure of sampled gratings are investigated.