In order to solve the problems of oscillation on the top and side lobes of reflection spectrum for linear chirped grating

the influences of refractive index modulation depth

grating length

chirp coefficient on reflection spectrum are studied based on coupled mode theory

and the relationship between parameters and characteristics are deeply explored in this paper.A asymmetric apodized optimization method based on refractive index compensation is proposed.The effective apodization functions

compensation factor and optimal piecewise apodization ratio are also explored.Simulation results show that the peak shifts to the direction of longer wavelength

and the 3 dB bandwidths increase basically linear with L（5

1

00 mm）

Δn(10

-5

1

0

-3

)and C（0.01

0

.2 nm/cm）

which can achieve 1.79

1.26

1.71 nm

respectively.The peak value increases with LandΔn

and decreases with C.There is a big shock at the top when Lis small.WhenΔnis large

obvious side lobes appear on both sides of the central spectrum.After applying the optimization algorithm

the linear region has increased

and the dispersion curve has been more stable.Compared to the traditional algorithm

the top of reflection spectrum is much more flat with no side lobe and no bandwidth reduction.The proposed optimization algorithm shows the better optical characteristics.