Frequency chirp correction method for photonic time-stretch system

Patent metadata

Field	Value
Publication number	US-10979143-B2
Application number	US-202016789431-A
Country	US
Kind code	B2
Filing date	Feb 13, 2020
Priority date	Feb 26, 2019
Publication date	Apr 13, 2021
Grant date	Apr 13, 2021

Abstract

A frequency chirp correction method for the photonic time-stretch system comprises acquiring the stretching signal, i.e. acquiring the time-domain data after the time-domain stretching. First, the time-domain data of the stretching signal is Fourier transformed to obtain the spectral distribution. The spectral distribution is then convoluted with the first frequency-domain correction factor, and then multiplied with the second frequency-domain correction factor to obtain the modified frequency spectrum. Finally, the modified frequency spectrum is performed by the inverse Fourier transform to obtain the time-domain signal after the frequency chirp correction.

First claim

What is claimed is:

1. A frequency chirp correction method for a photonic time-stretch system, comprising:
(1) acquiring a photocurrent signal by an analog to digital converter outputted by a fiber;
(2) transforming the photocurrent signal from a time-domain to a frequency-domain representation through Fourier transform, to obtain a frequency spectrum signal;
(3) applying two frequency-domain correction factors H 1 (ω) and H 2 (ω) to modify the frequency spectrum signal;
(4) performing the inverse Fourier transform on the modified frequency spectrum signal to obtain a photocurrent signal in time-domain representation after the frequency chirp corrections;
wherein an expression of the frequency-domain correction factor H 1 (ω) is as follows:

H
1

⁡

(
ω
)

=

exp
⁡

(

-

ω
2

2
⁢

ω
d
2

)

·

[

τ
1

⁡

(
ω
)

⁢

L
1

+

τ
2

⁡

(
ω
)

⁢

L
2

]

wherein, ω represents an angular frequency, ω d represents a frequency width filtered by an optical filter in the system, L 1 is a length of a first optical fiber in the system, τ 1 (w) is a group delay per unit length corresponding to the first optical fiber under the angular frequency ω, L 2 is a length of a second optical fiber in the system, and τ 2 (ω) is a group delay per unit length corresponding to the second optical fiber under the angular frequency ω.

2. The frequency chirp correction method according to claim 1 , wherein the expression of the photocurrent signal in step (1) is as follows:

I
⁡

(
t
)

=

A
2

⁢

{

exp
⁡

[

j
⁢

ω
RF

⁢
t

M
⁡

(
t
)

]

+

exp
⁡

[

-
j

⁢

ω
RF

⁢
t

M
⁡

(
t
)

]

}

wherein, A and ω RF represent an amplitude and angular frequency of a microwave signal inputted by the system, respectively; j represents an imaginary unit; l(t) represents a photocurrent signal, t represents time, and M (t) represents a time-domain stretch multiple of the system related to time.

3. The frequency chirp correction method according to claim 1 , wherein the process of modifying the frequency signal in the step (3) is: performing convolution on the frequency spectrum signal with the frequency-domain correction factor H 1 (ω), and then multiplying a convolution result with the frequency-domain correction factor H 2 (ω) to obtain the modified frequency spectrum signal.

4. The frequency chirp correction method according to claim 1 , wherein the expression of the corrected photocurrent signal in step (4) is as follows:

I
′

⁡

(
t
)

=

A
⁢

⁢

cos
⁡

(

ω
RF

⁢
t

M

)

wherein A

Assignees

• Univ Zhejiang

Inventors

• Liu Changqiao
• Jin Xiaofeng
• Yu Xianbin
• Jin Xiangdong
• Zhang Xianmin
• Zheng Shilie
• Tan Qinggui
• Cong Bo

Classifications

• H04B10/25133 Primary

  including a lumped electrical or optical dispersion compensator (H04B10/2519, H04B10/2525 takes precedence) · CPC title

• H04B10/2513

  due to chromatic dispersion · CPC title

• H01S3/0085

  Modulating the output, i.e. the laser beam is modulated outside the laser cavity · CPC title

• H01S3/0078

  Frequency filtering · CPC title

• H04B10/2543

  due to fibre non-linearities, e.g. Kerr effect · CPC title