CN110200578B

CN110200578B - All-fiber inner snoop head based on mechanical long-period fiber grating

Info

Publication number: CN110200578B
Application number: CN201910418373.3A
Authority: CN
Inventors: 张明; 王安安; 杜颖
Original assignee: Zhejiang University of Technology ZJUT
Current assignee: Zhejiang University of Technology ZJUT
Priority date: 2019-05-20
Filing date: 2019-05-20
Publication date: 2024-05-07
Anticipated expiration: 2039-05-20
Also published as: CN110200578A

Abstract

The utility model provides a full optical fiber inner snoop head based on long period fiber grating of mechanical system, includes input optical fiber, the long period fiber grating MLPFG of mechanical system, two pairs of steel needles that put the position different in front and back, inhomogeneous atress optic fibre NSF and one section graded index optic fibre GIF, the long period fiber grating MLPFG of mechanical system is located in the fiber core of input optical fiber, inhomogeneous atress optic fibre NSF welds behind the input optical fiber, graded index optic fibre GIF welds behind inhomogeneous atress optic fibre NSF. The invention realizes full-optical-fiber endoscopic imaging with large focal depth and as large as possible transverse resolution.

Description

All-fiber inner snoop head based on mechanical long-period fiber grating

Technical Field

The invention relates to the technical field of medical detection and the field of mechanical long-period fiber gratings (MECHANICALLY INDUCED LONG-Period Fiber Gratings, abbreviated as MLPFG), in particular to an all-fiber endoscopic probe.

Background

The main function of the all-fiber probe is to conduct the light beam emitted by the light source, focus the light beam in the tissue of the sample, and then scan and collect the reflected light of the sample for imaging. Since the design of the first endoscopic probe has been proposed, there have been a wide variety of endoscopic probes, which can be classified into side-looking endoscopic probes and front-looking endoscopic probes. Side view endoscopy is suitable for imaging of a large inner cavity, is also the most mainstream endoscopic imaging mode at present, and front view endoscopy is more suitable for image-guided biological biopsy, for example, front view endoscopy is often adopted when imaging of bladder, ovary and the like.

Disclosure of Invention

In order to overcome the defects of the existing endoscopic probe, the invention provides an all-fiber endoscopic probe based on a mechanically-made long-period fiber bragg grating, which realizes all-fiber endoscopic imaging with large focal depth and as large a transverse resolution as possible.

The technical scheme adopted for solving the technical problems is as follows:

An all-fiber inner snoop head based on a mechanical long period fiber grating comprises an input fiber, a mechanical long period fiber grating MLPFG, a front pair of steel needles and a rear pair of steel needles with different placement positions, a non-uniform stress fiber (Nonuniform Stressed Fiber, abbreviated as NSF) and a section of graded index fiber (Graded Index Fiber, abbreviated as GIF), wherein the mechanical long period fiber grating MLPFG is positioned in the fiber core of the input fiber, the non-uniform stress fiber NSF is welded behind the input fiber, and the graded index fiber GIF is welded behind the non-uniform stress fiber NSF.

Further, the previous pair of steel pins are grooved, applying pressure to the input fiber to form an MLPFG; the latter pair of steel needles are positioned outside the unevenly stressed optical fiber, and apply pressure F2.

The front pair of steel needles are arranged at the upper and lower positions, and the rear pair of steel needles are arranged at the left upper and right lower positions. An angle theta is arranged between the front and back pairs of steel needle planes so as to regulate and control the light field, and a high-order mode is selected to realize the beam expansion collimation output of the light field.

Still further, the light after beam expansion and collimation is focused in the sample through the graded index optical fiber, so that the imaging with large focal depth is realized, and meanwhile, the transverse resolution as large as possible is ensured, and the information of the sample is obtained.

The technical conception of the invention is as follows: by welding a section of NSF after the MLPFG and welding the GIF after the NSF, the all-fiber inner snoop head with controllable light field distribution based on the MLPFG is manufactured. The high-order mode is selected by using a mechanical long-period fiber bragg grating, the beam expansion and collimation output of the optical field is realized, and the imaging with large focal depth and proper transverse resolution is finally realized by combining the graded index fiber.

The beneficial effects of the invention are mainly shown in the following steps: 1) The beam expansion collimation output of the optical field is realized while the inter-mode interference is reduced by utilizing the coupling light splitting characteristic of the mechanical long period fiber grating and the optical field regulation function of NSF. 2) The graded index optical fiber replaces a lens in the traditional endoscope probe, and the volume of the optical fiber probe is greatly reduced.

Drawings

FIG. 1 is a schematic diagram of an all-fiber inner snoop head based on a mechanically-made long-period fiber grating.

Fig. 2 is a schematic view of two pairs of steel needle placement positions.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Referring to fig. 1 and 2, an all-fiber endo-snoop head based on a mechanically long-period fiber grating includes an input fiber 101, a mechanically long-period fiber grating MLPFG102, a non-uniform stress fiber NSF103 and a graded-index fiber GIF104, wherein the mechanically long-period fiber grating MLPFG102 is located in the core of the input fiber 101, the non-uniform stress fiber NSF103 is welded to the input fiber 101, and the graded-index fiber GIF104 is welded to the non-uniform stress fiber NSF 103. The former pair of steel needles are provided with grooves and are positioned on the outer side of the input optical fiber 101, and pressure F1 is applied, so that a mechanically-made long-period fiber grating MLPFG102 is formed; the latter pair of steel needles is located outside the unevenly stressed fiber 103, exerting a pressure F2. The front pair of steel needles are arranged at the upper and lower positions, and the rear pair of steel needles are arranged at the left upper and right lower positions. As shown in FIG. 2, an angle theta is formed between the front and rear pairs of steel needle planes so as to regulate and control the light field, select high-order modes, reduce the interference between modes and realize the beam expansion collimation output of the light field. The expanded collimated light is focused into the sample 105 through graded index fibers to achieve a large depth of focus and as large lateral resolution as possible (beam as shown at 116) to obtain sample information.

Referring to fig. 1, the overall device operation and principle is as follows: the light source is selected to be a low coherence continuous broad spectrum light source that produces the LP01 signal shown as 111 in fig. 1 and whose spectral diagram is shown as 1 in fig. 1.

The LP01 signal passes through the MLPFG102 and part of the energy of the optical signal is coupled into the cladding mode LP11 due to the coupling characteristics of the MLPFG, as shown at 112 in fig. 1, the spectral distribution is 2 (in the core), 3 (in the cladding) in fig. 1, respectively, i.e. the fundamental mode in the fiber is partially coupled into the higher order modes in the cladding. The MLPFG is designed according to actual requirements, so that the coupling bandwidth of the MLPFG is larger than the effective wavelength bandwidth of the light source, and the MLPFG has the coupling efficiency meeting the requirements and meets the subsequent imaging requirements.

The high order mode LP11 optical signal coupled into the cladding through the MLPFG102 continues to propagate forward, and the pressure of the steel against the core as it passes through the NSF causes the refractive index of the core to change, which causes the LP11 mode to form a phase difference in both directions as it propagates in the fiber. The LP11 mode is thus split into two modes, referred to as LP11a and LP11b. By adjusting the steel needle pressure and theta, the phase difference between the LP11a and the LP11b and the included angle of two modes of transmission can be adjusted, so that the beam expansion and collimation of the transmitted light are realized, and finally, a beam 113 with uniform section intensity distribution (consisting of 114 and 115 in figure 1 and the spectrogram respectively corresponding to 4 and 5) is obtained. And then the sample 105 is focused through the graded index optical fiber 104, so that large focal depth imaging is realized, and meanwhile, the transverse resolution as large as possible is ensured, and the sample information is obtained.

Claims

1. The all-fiber endoscopic probe based on the mechanical long-period fiber bragg grating is characterized by comprising an input fiber, a mechanical long-period fiber bragg grating MLPFG, a front steel needle, a rear steel needle, a non-uniform stress fiber NSF and a section of graded index fiber GIF, wherein the front steel needle and the rear steel needle are different in placement positions, the mechanical long-period fiber bragg grating MLPFG is positioned in a fiber core of the input fiber, the non-uniform stress fiber NSF is welded behind the input fiber, and the graded index fiber GIF is welded behind the non-uniform stress fiber NSF;

The front pair of steel needles are provided with grooves, and pressure is applied to the input optical fiber so as to form a mechanically-made long-period fiber grating MLPFG; the latter pair of steel needles are positioned outside the unevenly stressed optical fibers, and pressure F2 is applied; the front pair of steel needles are arranged at upper and lower positions, the rear pair of steel needles are arranged at left, upper, right and lower positions, and an angle theta is formed between the planes of the front pair of steel needles and the rear pair of steel needles;

after the LP01 signal generated by the low-coherence continuous wide-spectrum light source passes through the mechanically long-period fiber grating MLPFG, part of energy of the optical signal is coupled into the cladding mode LP11 due to the coupling characteristic of the mechanically long-period fiber grating MLPFG, when the optical fiber NSF passes through the non-uniform stress fiber, the refractive index of the fiber core can be changed by the pressure of the steel needle on the fiber core, and a certain phase difference is formed in two directions when the LP11 mode propagates in the optical fiber due to the change of the refractive index of the fiber core, so that the LP11 mode is separated into two modes, namely LP11a and LP11b; by adjusting the pressure and theta of the steel needle, the phase difference between the LP11a and the LP11b and the included angle of two modes of transmission can be adjusted, so that the beam expansion collimation of the transmitted light is realized.

2. The all-fiber endoscope probe based on the mechanically-made long-period fiber bragg grating according to claim 1, wherein the light after beam expansion and collimation is focused in a sample through a graded index fiber GIF to obtain sample information.