CN211825682U - Optical domain frequency sweeping device based on FP cavity interferometer - Google Patents
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Abstract
The utility model discloses an optical domain frequency sweeping device based on FP cavity interferometer, a sine trigger voltage signal generated by a clock signal source is input into a radio frequency amplifier; the radio frequency amplifier amplifies and converts the sinusoidal trigger voltage signal into a current driving signal and inputs the current driving signal to the direct modulation laser; after the direct modulation laser is modulated by a current driving signal, seed pulse laser with a broad spectrum is generated and is input into a first port of an optical circulator, and then is input into an FP cavity interferometer through a second port of the optical circulator; the FP cavity interferometer widens the seed pulse laser to make different frequency spectrums of the seed pulse laser generate linear delay to form sweep frequency laser, the sweep frequency laser is output from a third port of the optical circulator through a second port of the optical circulator and then is input into the optical amplifier; the optical amplifier amplifies the sweep-frequency laser to form sweep-frequency laser output with certain power. The utility model discloses a need not the mechanical structure of tradition sweep frequency laser instrument, the reliability is superior to than tradition sweep frequency laser source to easily realize.
Description
Technical Field
The utility model relates to a frequency sweep light source technical field, concretely relates to optical domain frequency sweep device and method based on FP (Fabry-Perot) cavity interferometer.
Background
Optical Coherence Tomography (OCT) is an imaging technique rapidly developed in the last decade, which uses the basic principle of weak coherent Optical interferometer to detect back-reflected or several scattered signals of incident weak coherent light at different depth levels of biological tissue, and scans to obtain two-dimensional or three-dimensional structural images of biological tissue. In addition to their use in the medical field, optical coherence tomography is advancing towards other fields, in particular industrial measurement fields, such as displacement sensors, thickness measurement of thin substrates and other measurements of measured objects that can be converted into displacements.
With the further development of the technology, the requirements for the resolution of the optical tomography are increasing. The present frequency sweep device for optical coherence tomography consists of a wide spectrum laser source, an adjustable filter (such as a fiber grating) and a function generator. The wide-spectrum laser output by the wide-spectrum laser light source is sent into the adjustable filter, and the adjustable filter controls the wide-spectrum laser light source under the control of the function generator so as to output the swept-frequency laser. Because all wavelength components of the wide-spectrum laser light source of the existing frequency sweeping device are output simultaneously, and all the wavelength components need to be filtered out at different times through the tunable filter to realize the scanning of the laser frequency, namely the linearity of the laser frequency sweeping needs to depend on the tuning linearity of the tunable filter, however, the tuning linearity of the tunable filter is greatly influenced by the external environment, so that in practical application, the reliability of the linearity of the laser frequency sweeping of the existing frequency sweeping device is poor, and the testing precision of the OCT is influenced.
SUMMERY OF THE UTILITY MODEL
The utility model aims to solve is that current optical coherence tomography's sweep frequency linearity receives the environmental impact and the reliability is not good to influence OCT's measuring accuracy's problem, provide an optical domain sweep frequency device based on FP chamber interferometer.
In order to solve the above problems, the utility model discloses a realize through following technical scheme:
an optical domain frequency sweeping device based on an FP (Fabry-Perot) cavity interferometer comprises a clock signal source, a radio frequency amplifier, a direct modulation laser, an optical circulator, the FP cavity interferometer and an optical amplifier; a sinusoidal trigger voltage signal generated by a clock signal source is input to a radio frequency amplifier; the radio frequency amplifier amplifies and converts the sinusoidal trigger voltage signal into a current driving signal and inputs the current driving signal to the direct modulation laser; after the direct modulation laser is modulated by a current driving signal, seed pulse laser with a broad spectrum is generated and is input into a first port of an optical circulator, and then is input into an FP cavity interferometer through a second port of the optical circulator; the FP cavity interferometer widens the seed pulse laser to make different frequency spectrums of the seed pulse laser generate linear delay to form sweep frequency laser, the sweep frequency laser is output from a third port of the optical circulator through a second port of the optical circulator and then is input into the optical amplifier; the optical amplifier amplifies the sweep-frequency laser to form sweep-frequency laser output with certain power.
As an improvement, the optical domain frequency sweeping device based on the FP cavity interferometer further comprises a temperature controller and/or a power controller; the temperature controller is connected with the directly modulated laser through a temperature control cable and is used for controlling the temperature of the directly modulated laser and realizing the stable output of the wavelength of the swept laser; the power controller is connected with the directly modulated laser through a power control cable and is used for controlling the power of the directly modulated laser and realizing the stable output of the power of the sweep frequency laser.
In the above scheme, the FP cavity interferometer is composed of two parallel reflectors, wherein the reflectivity r of the front reflector1Less than 1, the rear reflector reflectivity is 1; the dispersion correlation coefficient of the FP cavity interferometer is 0.1 multiplied by 10-26ps2To 10X 10-26ps2In the meantime.
Compared with the prior art, the utility model has the characteristics of as follows:
1. based on a direct modulation laser, wide spectrum seed pulse laser is generated, and the repetition frequency is higher than that of a traditional mechanical frequency sweeping laser source;
2. the seed pulse laser is broadened through the dispersion effect of the FP cavity interferometer, so that different frequency spectrums of the seed pulse laser generate linear delay, a mechanical structure of a traditional frequency sweeping laser is not needed, and the reliability is superior to that of a traditional frequency sweeping laser source;
3. the existing mature optical device is adopted, and the realization is easy.
Drawings
FIG. 1 is a block diagram of an optical domain frequency sweeping device based on an FP cavity interferometer; in the figure, solid-line connecting lines represent optical fiber connections, and dashed-line connecting lines represent electrical signal connections.
Fig. 2 is a schematic diagram of the wavelength components of the seed pulse laser output by the directly modulated laser.
FIG. 3 is a schematic diagram of the wavelength components of the swept laser output by the FP cavity interferometer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the following specific examples.
An optical domain frequency sweeping device based on an FP (Fabry-Perot) cavity interferometer is shown in figure 1 and comprises a clock signal source, a radio frequency amplifier, a direct modulation laser, an optical circulator, the FP cavity interferometer, an optical amplifier, a temperature controller and a power controller.
The clock signal source is used for generating a sine trigger voltage signal, and the current amplitude of the clock signal source is larger than the gain sensitivity of the radio frequency amplifier.
The radio frequency amplifier is used for converting the voltage signal generated by the clock signal source into a current driving signal and modulating the direct modulation laser.
The directly modulated laser is used for generating seed pulse laser. When the current driving signal is lower than the light emitting threshold of the directly modulated laser, the gain is closed, and no laser is emitted; when the current driving signal is higher than the light emitting threshold of the directly modulated laser, the gain is turned on, the directly modulated laser can generate relaxation oscillation, the first peak of the relaxation oscillation is usually narrow in pulse width, and seed pulse laser of tens of ps in time domain and tens of GHz in frequency domain can be generated.
The optical circulator is used for separating the seed pulse laser and the sweep frequency laser, transmitting the seed pulse laser of the input port 1 to the port 2 for output, and transmitting the sweep frequency laser of the input port 2 to the port 3.
The FP cavity interferometer is used for widening seed pulse laser, the reflectivity of the FP cavity interferometer is 1, different frequency spectrums of the seed pulse laser generate linear delay, sweep frequency laser is formed, and the sweep frequency of an optical domain is achieved.
And the optical amplifier is used for amplifying and outputting the power of the swept laser.
And the temperature controller is used for controlling the temperature of the direct modulation laser and realizing the stable output of the swept laser wavelength.
And the power controller is used for controlling the power of the direct modulation laser and realizing the stable output of the power of the sweep frequency laser.
A sine trigger voltage signal generated by a clock signal source is input into a radio frequency amplifier through a radio frequency transmission line, the radio frequency amplifier amplifies and converts the sine trigger voltage signal into a current drive signal and inputs the current drive signal into a direct modulation laser through the radio frequency transmission line, the direct modulation laser generates wide-spectrum seed pulse laser after being modulated by the current drive signal and then inputs the wide-spectrum seed pulse laser into a first port of an optical circulator through an optical fiber, the wide-spectrum seed pulse laser is connected with an FP (Fabry-Perot) cavity interferometer through the second port of the optical circulator through the optical fiber, the FP cavity interferometer expands the seed pulse laser to enable different spectrums of the seed pulse laser to generate linear delay to form swept laser, the swept laser passes through a second port of the optical circulator and then is output through a third port of the optical circulator and then is transmitted to the optical amplifier through the optical fiber to be amplified, and the swept laser with certain power is output through. The temperature controller is connected with the directly modulated laser through a temperature control cable and is used for controlling the temperature of the directly modulated laser and realizing the stable output of the wavelength of the swept laser. The power controller is connected with the directly modulated laser through a power control cable and is used for controlling the power of the directly modulated laser and realizing the stable output of the power of the sweep frequency laser.
The operation method of the optical domain frequency sweeping device comprises the following steps:
The clock signal source generates a periodic sinusoidal voltage signal, the frequency range of the periodic sinusoidal voltage signal is 1 MHz-155 MHz, the current amplitude is larger than the gain sensitivity of the radio frequency amplifier, and the periodic sinusoidal voltage signal is input to the radio frequency amplifier.
And 2, converting a voltage signal generated by the clock signal source into a current driving signal by the radio frequency amplifier to modulate the direct-tuned laser.
The amplitude value range of the current driving signal generated by the radio frequency amplifier is 2 times to 5 times of the current threshold value of the directly modulated laser, so that the directly modulated laser generates a gain switch effect and generates an optical pulse signal with a wide spectrum.
And 3, outputting seed pulse laser by the direct-modulated laser under the drive of the current drive signal.
The directly modulated laser generates a gain switching effect under the modulation of a driving signal with a current threshold value of more than 2 times and less than 5 times, and outputs an optical pulse with a spectrum of E (ω), where the spectrum of the optical pulse can be represented by the following formula:
E(ω)＝FFT{exp(-at2)exp[i(ω0t+bt2)]} (1)
where a represents the pulse time-domain width parameter, t represents time, and i represents the unit of an imaginary number
ω0Represents the center frequency of the pulse spectrum, b represents the pulse chirp parameter, and FFT {. cndot.) represents the fourier transform.
And 4, in the process of outputting the pulse spectrum by the directly modulated laser, controlling the temperature and the power of the directly modulated laser by the temperature controller and/or the power controller so as to realize stable output of the power of the frequency sweeping laser.
In the gain switching process, the temperature controller controls the temperature of the directly modulated laser within the range of 25 +/-0.01 ℃, and the power controller controls the output power stability of the directly modulated laser within the range of +/-0.01 dBm, so that the wavelength stability of the laser is within the range of +/-1 pm.
And 5, the directly modulated laser transmits the output seed pulse laser to the FP cavity interferometer through the optical circulator.
And 6, widening the seed pulse laser by the FP cavity interferometer by using the dispersion characteristic of the FP cavity interferometer, and linearly delaying different frequency spectrums of the seed pulse laser to form swept-frequency laser.
The FP cavity interferometer consists of two parallel reflectors, the reflectivity r of the front reflector1Less than 1 and a rear mirror reflectivity of 1.
Optical pulse spectrum E output by FP cavity interferometerFP(ω) can be expressed as:
EFP(ω)＝E(ω)·H(ω) (2)
where H (ω) is the FP cavity interferometer frequency domain response function, which can be expressed as:
where ω denotes the light source frequency, A denotes the attenuation coefficient of the FP cavity, n denotes the FP cavity refractive index, d denotes the FP cavity thickness, f (nd, r)1) Represents the dispersion correlation coefficient of the FP cavity interferometer, the value of which is related to the refractive index, thickness and front reflection of the FP cavityThe mirror reflectivity is relevant.
By designing the refractive index n, the thickness d and the front mirror reflectivity r of the FP cavity1So that the dispersion correlation coefficient f (nd, r) of the FP cavity interferometer1) At 0.1X 10-26ps2To 10X 10-26ps2And the second port of the optical circulator outputs different pulse components of the light pulse input to the FP cavity interferometer to obtain linear time delay to form swept-frequency laser.
Fig. 2 is a schematic diagram of wavelength components of seed pulse laser output by the directly tuned laser, and fig. 3 is a schematic diagram of wavelength components of swept laser output by the FP cavity interferometer. The ordinate in the figure is the wavelength of the light of the pulse in nm, and the abscissa is the pulse time coordinate in ps, to clearly show the sweep of the pulse. Wherein a is 5 × 10-3ps-2，b＝2.5×10-4ps-2，ω0＝1.21488×1015Hz，f(nd,r1)＝1×10-26ps2From the figure, one can obtain: through the effect of the FP cavity interferometer, laser with the width of 49nm output by the directly modulated laser can be compressed to 35nm, the scanning time is widened to 1500ns from 165ps, and the sweep slope of the light source is about 0.023nm/ps, so that the sweep output with a long period is realized.
And 7, sending the swept-frequency laser to an optical amplifier through an optical circulator by the FP cavity interferometer, and outputting the swept-frequency laser to a subsequent optical coherence tomography scanner for interference imaging after the swept-frequency laser is amplified by the optical amplifier.
The optical amplifier compensates the loss of pulse energy in the broadening process of the FP cavity interferometer, and outputs an optical pulse with frequency (wavelength) linearly changing along with time on a frequency domain, so as to sweep frequency of the existing optical domain.
It should be noted that, although the above-mentioned embodiments of the present invention are illustrative, the present invention is not limited thereto, and therefore, the present invention is not limited to the above-mentioned embodiments. Other embodiments, which can be made by those skilled in the art in light of the teachings of the present invention, are considered to be within the scope of the present invention without departing from the principles thereof.
Claims (3)
1. An optical domain frequency sweeping device based on an FP (Fabry-Perot) cavity interferometer is characterized by comprising a clock signal source, a radio frequency amplifier, a directly modulated laser, an optical circulator, the FP cavity interferometer and an optical amplifier;
a sinusoidal trigger voltage signal generated by a clock signal source is input to a radio frequency amplifier; the radio frequency amplifier amplifies and converts the sinusoidal trigger voltage signal into a current driving signal and inputs the current driving signal to the direct modulation laser; after the direct modulation laser is modulated by a current driving signal, seed pulse laser with a broad spectrum is generated and is input into a first port of an optical circulator, and then is input into an FP cavity interferometer through a second port of the optical circulator; the FP cavity interferometer widens the seed pulse laser to make different frequency spectrums of the seed pulse laser generate linear delay to form sweep frequency laser, the sweep frequency laser is output from a third port of the optical circulator through a second port of the optical circulator and then is input into the optical amplifier; the optical amplifier amplifies the sweep-frequency laser to form sweep-frequency laser output with certain power.
2. The optical domain frequency sweeping device based on the FP cavity interferometer of claim 1 further comprising a temperature controller and/or a power controller;
the temperature controller is connected with the directly modulated laser through a temperature control cable and is used for controlling the temperature of the directly modulated laser and realizing the stable output of the wavelength of the swept laser;
the power controller is connected with the directly modulated laser through a power control cable and is used for controlling the power of the directly modulated laser and realizing the stable output of the power of the sweep frequency laser.
3. The optical domain frequency sweeping device based on the FP cavity interferometer of claim 1, wherein the FP cavity interferometer is composed of two parallel reflectors, wherein the reflectivity r of the front reflector1Less than 1, the rear reflector reflectivity is 1; the dispersion correlation coefficient of the FP cavity interferometer is 0.1 multiplied by 10-26ps2To 10X 10-26ps2In the meantime.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110927114A (en) * | 2019-11-22 | 2020-03-27 | 中国电子科技集团公司第三十四研究所 | Optical domain frequency sweeping device and method based on FP (Fabry-Perot) cavity interferometer |
| CN114487478A (en) * | 2022-01-26 | 2022-05-13 | 西安交通大学 | MOEMS acceleration sensor system based on quadrature carrier modulation |
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2019
- 2019-11-22 CN CN201922035233.6U patent/CN211825682U/en not_active Withdrawn - After Issue
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110927114A (en) * | 2019-11-22 | 2020-03-27 | 中国电子科技集团公司第三十四研究所 | Optical domain frequency sweeping device and method based on FP (Fabry-Perot) cavity interferometer |
| CN110927114B (en) * | 2019-11-22 | 2023-12-29 | 中国电子科技集团公司第三十四研究所 | Optical domain frequency sweeping device and method based on FP cavity interferometer |
| CN114487478A (en) * | 2022-01-26 | 2022-05-13 | 西安交通大学 | MOEMS acceleration sensor system based on quadrature carrier modulation |
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