CN113008391B - Power coupling coefficient characterization method based on time domain pulse - Google Patents
Power coupling coefficient characterization method based on time domain pulse Download PDFInfo
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Abstract
The invention relates to a method for representing a power coupling coefficient based on a time domain pulse, which comprises the following steps: measuring time domain impulse response between two adjacent modes of the weak coupling optical fiber with the length L; carrying out region division on the measured time domain impulse response according to power distribution to obtain an integral value of an excitation mode time peak and an integral value of a weak coupling time platform between optical fiber modes; respectively carrying out integral calculation on the integral value of the excitation mode time peak and the integral value of the weak coupling time platform to obtain a power coupling coefficient; the method for representing the calculation of the time domain impulse response power according to the regional integral has extremely high tolerance on pulse broadening caused by intra-mode dispersion, phase noise and bandwidth limitation of a measurement system, effectively inhibits the influence on calculating the power coupling coefficient caused by the internal power fluctuation of a weak coupling time platform caused by distributed mode coupling and noise, and obtains a more accurate power coupling coefficient between modes.
Description
Technical Field
The invention relates to the technical field of optical communication, in particular to a power coupling coefficient characterization method based on time domain pulse.
Background
With the continuous development of the information-oriented society and the increasing information demand, the capacity of the current commercial single-mode optical fiber communication system approaches the nonlinear shannon limit capacity. In recent years, a mode division multiplexing transmission system based on a multimode/few-mode optical fiber is considered as a scheme effective for increasing the communication capacity of the system. On the one hand, mode-to-mode coupling is inevitably generated in optical fiber transmission due to random fluctuations of the optical fiber in the longitudinal direction caused by the drawing and laying processes of the optical fiber, so that the mode division multiplexing system usually requires high-complexity multiple-input multiple-output (MIMO) equalization. In order to avoid MIMO equalization or reduce the complexity of MIMO equalization, a low-complexity mode division multiplexing communication system can be realized by designing a few-mode fiber with weak coupling characteristics between modes (groups).
On the other hand, the characterization results of the existing weak coupling optical fiber characterization methods, such as the direct system power measurement characterization method or the time domain impulse response fitting characterization method, are often highly dependent on the performance of the equipment used in the measurement device, and the characterization results of different methods are very different for weak coupling few-mode optical fibers with similar refractive index distribution, even for a specific optical fiber.
In the prior art, chinese patent CN109449731B discloses an ultrafast pulsed fiber laser, which is published as 20/09/2019 and includes an optical fiber mode-locked laser source, a pulse stretcher, a pulse laser amplifier, and a pulse compressor, wherein pulse laser emitted from the optical fiber mode-locked laser source is subjected to dispersion by the pulse stretcher to generate time-domain stretching, is subjected to energy amplification by the pulse laser amplifier, and is finally compressed in time domain by the pulse compressor to a required pulse laser output with a picosecond or femtosecond pulse width, an output end of the optical fiber mode-locked laser source is connected to an input end of the pulse stretcher, an output end of the pulse stretcher is connected to an input end of the pulse laser amplifier, and an output end of the pulse laser amplifier is connected to an input end of the pulse compressor. The laser in the scheme emits pulses to generate time domain broadening, the optical fiber of the laser is different from that of the laser, the weak coupling optical fiber is adopted in the laser, and the purpose and the technical details are different.
Disclosure of Invention
The invention provides a method for representing a power coupling coefficient based on time domain pulse, aiming at solving the technical defect that the representation of power coupling depends on the performance of equipment in the existing weak coupling optical fiber.
In order to realize the purpose of the invention, the technical scheme is as follows:
a method for characterizing a power coupling coefficient based on a time domain pulse comprises the following steps:
s1: measuring time domain impulse response between two adjacent modes of the weak coupling optical fiber with the length L;
s2: dividing the measured time domain impulse response into regions according to power distribution to obtain an integral value of an excitation mode time peak and an integral value of a weak coupling time platform between optical fiber modes;
s3: and respectively carrying out integral calculation on the integral value of the excitation mode time peak and the integral value of the weak coupling time platform to obtain the power coupling coefficient.
In the scheme, the method for characterizing the inter-mode distributed coupling caused by optical fiber transmission is effectively distinguished, the characterization method of time domain pulse response power calculation according to the regional integral has extremely high tolerance on pulse broadening caused by intra-mode dispersion, phase noise and measurement system bandwidth limitation, and the influence on calculating the power coupling coefficient caused by the internal power fluctuation of a weak coupling time platform caused by distributed mode coupling and noise is effectively inhibited, so that the more accurate inter-mode power coupling coefficient is obtained.
In step S1, the method for measuring the time-domain impulse response includes a swept spectrum interferometer method or other method for measuring the time-domain impulse response of the optical fiber.
The measuring method of the time domain impulse response also comprises a vector network analyzer method.
The measuring method of the time domain impulse response comprises other methods for measuring the time domain impulse response of the optical fiber.
In step S2, the measured time domain impulse response is time-domain divided according to the power distribution over time, so as to obtain the weak coupling time plateau between the excitation mode time peak and the fiber mode.
In step S3, the power crosstalk caused by the distributed coupling between the two modes during the optical fiber transmission process is calculated according to the integral value of the time peak of the excitation mode and the integral value of the weak coupling time platform, and the power coupling coefficient between the modes is obtained through the power crosstalk.
The power crosstalk XT is obtained by the following algorithm:
total power P of excitation patternsIntegral value representing time peak of excitation mode, total power P of distributed couplingcThe integral value representing the weak coupling time plateau.
Distributed coupled total power PcThe total power in the range of the differential mode group delay caused by weak coupling between two modes in the optical fiber transmission process.
The power coupling coefficient is obtained by the following algorithm:
where arctanh represents the inverse hyperbolic tangent function.
The time peaks of the power crosstalk caused by non-ideal mode conversion or multiplexing devices are distinguished in time, and the influence on the integral calculation is eliminated.
In the scheme, the method and the device can effectively distinguish the mode-to-mode distributed coupling caused by optical fiber transmission and the crosstalk caused by a non-ideal mode converter or a multiplexer, so that a more accurate mode-to-mode power coupling coefficient is obtained.
The characterization method of time domain pulse response power according to time region integral calculation provided by the invention has extremely high tolerance on pulse broadening caused by intra-mode dispersion, phase noise and measurement system bandwidth limitation, namely, the influence of the excitation mode peak no longer being an ideal impulse function on calculating the power coupling coefficient is inhibited, so that more accurate power coupling coefficient between modes is obtained.
The characterization method for calculating the impulse response power according to the time region integral can effectively inhibit the influence on the calculation of the power coupling coefficient caused by the internal power fluctuation of the weak coupling time platform due to the coupling of the distributed mode and noise, thereby obtaining the more accurate power coupling coefficient between the modes.
Compared with the prior art, the invention has the beneficial effects that:
the characterization method for the power coupling coefficient based on the time domain pulse effectively distinguishes the mode-to-mode distributed coupling caused by optical fiber transmission, has extremely high tolerance on pulse broadening caused by in-mode dispersion, phase noise and measurement system bandwidth limitation by the characterization method for calculating the time domain pulse response power according to the regional integral, and effectively inhibits the influence on the calculation of the power coupling coefficient caused by the internal power fluctuation of a weak coupling time platform caused by the distributed mode coupling and the noise, thereby obtaining more accurate mode-to-mode power coupling coefficient.
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FIG. 1 is a flow chart of a method of the present invention;
FIG. 2 is a diagram of the time domain impulse response power distribution between two weakly coupled modes according to the present invention.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent;
the invention is further illustrated below with reference to the figures and examples.
Example 1
As shown in fig. 1, a method for characterizing a power coupling coefficient based on a time domain pulse includes the following steps:
s1: measuring time domain impulse response between two adjacent modes of the weak coupling optical fiber with the length L;
s2: dividing the measured time domain impulse response into regions according to power distribution to obtain an integral value of an excitation mode time peak and an integral value of a weak coupling time platform among optical fiber modes;
s3: and respectively carrying out integral calculation on the integral value of the time peak of the excitation mode and the integral value of the weak coupling time platform to obtain a power coupling coefficient.
In the scheme, the method for characterizing the inter-mode distributed coupling caused by optical fiber transmission is effectively distinguished, the characterization method of time domain pulse response power calculation according to the regional integral has extremely high tolerance on pulse broadening caused by intra-mode dispersion, phase noise and measurement system bandwidth limitation, and the influence on calculating the power coupling coefficient caused by the internal power fluctuation of a weak coupling time platform caused by distributed mode coupling and noise is effectively inhibited, so that the more accurate inter-mode power coupling coefficient is obtained.
In step S1, the method for measuring the time-domain impulse response includes a swept spectrum interferometer method or other method for measuring the time-domain impulse response of the optical fiber.
The measuring method of the time domain impulse response also comprises a vector network analyzer method.
The measuring method of the time domain impulse response comprises other methods for measuring the time domain impulse response of the optical fiber.
In step S2, the measured time domain impulse response is time-domain divided according to the power distribution over time, so as to obtain the weak coupling time plateau between the excitation mode time peak and the fiber mode.
In step S3, the power crosstalk caused by the distributed coupling between the two modes during the optical fiber transmission process is calculated according to the integral value of the time peak of the excitation mode and the integral value of the weak coupling time platform, and the power coupling coefficient between the modes is obtained through the power crosstalk.
The power crosstalk XT is obtained by the following algorithm:
total power P of excitation modesIntegral value representing time peak of excitation mode, total power P of distributed couplingcThe integral value representing the weak coupling time plateau.
Distributed coupled total power PcThe total power in the range of the differential mode group delay caused by weak coupling between two modes in the optical fiber transmission process.
The power coupling coefficient is obtained by the following algorithm:
where arctanh represents the inverse hyperbolic tangent function.
The time peaks of the power crosstalk caused by non-ideal mode conversion or multiplexing devices are temporally differentiated, excluding the effect on the integration calculation.
Example 2
As shown in fig. 2, the time domain impulse response of transmission mode 1 sounding mode 2 and the time domain impulse response of transmission mode 2 sounding mode 2 are included. The invention measures the time domain impulse response between two adjacent modes of the weak coupling optical fiber with the length of L, and the measuring method of the time domain impulse response can be a spectrum scanning interferometer method, a vector network analyzer method or other methods which can measure the time domain impulse response of the optical fiber. The measured time domain impulse response shown in fig. 2 is divided into time regions according to the power distribution in time, wherein the region 1 is an excitation mode time peak, and the region 2 is a weak coupling time platform between optical fiber modes.
The integration calculations were performed for the excitation mode time peak of region 1 and the weak coupling time plateau of region 2, respectively. Wherein the integral value of the time peak of the excitation pattern represents the total power P of the excitation patternsThe integral value of the weak coupling time platform represents the total distributed coupling power P in the range of differential mode group delay caused by weak coupling between two modes in the optical fiber transmission processc. Whereas the cross-talk time peaks due to non-ideal mode conversion or (de) multiplexing devices can be temporally discriminated, thereby excluding their influence on the integration calculation.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (3)
1. A method for characterizing a power coupling coefficient based on a time domain pulse is characterized by comprising the following steps:
s1: measuring time domain impulse response between two adjacent modes of the weak coupling optical fiber with the length L;
s2: dividing the measured time domain impulse response into regions according to power distribution to obtain an integral value of an excitation mode time peak and an integral value of a weak coupling time platform between optical fiber modes;
s3: respectively carrying out integral calculation on the integral value of the excitation mode time peak and the integral value of the weak coupling time platform to obtain a power coupling coefficient;
in step S2, the measured time domain impulse response is divided into time regions according to the power distribution over time to obtain the integral value of the time peak of the excitation mode and the integral value of the weak coupling time plateau between the fiber modes;
in step S3, calculating power crosstalk caused by distributed coupling between two modes in the optical fiber transmission process according to the integral value of the excitation mode time peak and the integral value of the weak coupling time platform, and obtaining a power coupling coefficient between the modes through the power crosstalk;
the power crosstalk XT is obtained by the following algorithm:
total power P of excitation modesIntegral value representing time peak of excitation mode, total power P of distributed couplingcAn integral value representing a weak coupling time plateau;
distributed coupled total power PcThe total power in the differential mode group delay range caused by weak coupling between two modes in the optical fiber transmission process;
the power coupling coefficient is obtained by the following algorithm:
where arctanh represents the inverse hyperbolic tangent function.
2. The method for characterizing power coupling coefficients based on time-domain pulses as claimed in claim 1, wherein in step S1, the method for measuring the time-domain impulse response includes swept spectrum interferometer, vector network analyzer or other methods for measuring the time-domain impulse response of the optical fiber.
3. The method as claimed in claim 2, wherein the time peaks of the power crosstalk caused by the non-ideal mode conversion or the multiplexing device are temporally separated to exclude the influence on the integral calculation.
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