CN113777723A

CN113777723A - Compact optical signal monitoring light splitting detector

Info

Publication number: CN113777723A
Application number: CN202110927806.5A
Authority: CN
Inventors: 黄振东; 邱名武; 韦国辉
Original assignee: Xiamen San U Optronics Co ltd
Current assignee: Xiamen San U Optronics Co ltd
Priority date: 2021-08-13
Filing date: 2021-08-13
Publication date: 2021-12-10

Abstract

The invention discloses a compact optical signal monitoring and splitting detector, wherein an input optical fiber and an output optical fiber are single-mode optical fibers, a section of graded-index multimode optical fiber is welded at the end parts of the input optical fiber and the output optical fiber, and the end part of the graded-index multimode optical fiber presents a grinding angle theta₁The section of the light splitting lens is in a right trapezoid shape, and the inclined plane of the light splitting lens is parallel to the inclined plane of the end part of the graded-index multimode fiber; by adopting the scheme, the invention does not use a Green lens with higher cost and larger size, does not need to process a complicated beam splitting lens, and has the characteristics of simple structure, small volume and low cost.

Description

Compact optical signal monitoring light splitting detector

Technical Field

The invention relates to the technical field of optical communication, in particular to a photoelectric detector.

Background

Chinese patent CN 111290087 a discloses a spectroscopic detector, which includes an input/output portion, a spectroscopic lens, a detector chip and a sealing tube.

Chinese patent CN 107390329 a discloses a unidirectional TAP PD, which includes an input optical fiber, an optical fiber connector, a beam splitting lens, a detector assembly and an output optical fiber, wherein the input optical fiber and the output optical fiber are disposed in two holes of the optical fiber connector, and the beam splitting lens is disposed between the optical fiber connector and the detector assembly; the end, facing the optical fiber connector, of the light splitting lens is ground into an angle alpha, and the end, facing the detector assembly, of the light splitting lens is ground into an angle beta; the angles of alpha and beta are used to make the light input by the input end fiber vertical to the position where the beam splitting lens is not ground into the angle of beta and the light input by the output end fiber totally reflected at the position where the angle of beta is ground.

Because the light input by the optical fiber is sine wave instead of standard parallel light, the existing light splitting detectors all need a G-LENS LENS and a condensing LENS or a grinding angle sheet, so that the size of the detector is larger, and the high density degree of electronic components is difficult to improve; and the processing cost of the G-LENS and the angle grinding sheet is higher.

Disclosure of Invention

The invention aims to provide a small-sized, low-cost spectral detector for improving the high density of electronic components,

to achieve the above object, the present invention provides a compact optical signal monitoring and splitting detector, which comprises: the detector comprises an input/output part, a beam splitting lens, a detector chip and a sealing tube, wherein the input/output part comprises an input optical fiber and an output optical fiber, the input optical fiber and the output optical fiber are single-mode optical fibers, a section of graded-index multimode optical fiber is welded at the end parts of the input optical fiber and the output optical fiber, the length of the graded-index multimode optical fiber is odd times of the wavelength of an input light beam 1/4 of the input optical fiber, and the end part of the graded-index multimode optical fiber is a grinding angle theta₁The section of the beam splitter lens is in a right trapezoid shape, the inclined plane of the beam splitter lens is parallel to the inclined plane of the end part of the graded-index multimode fiber, and the vertical distance S between the two inclined planes is 1/2H sec theta₁cot[arcsin(nsinθ₁)]H is the distance between the centers of the two input and output optical fibers, and n is the refractive index; the relationship between the pitch of the GI multimode fiber and the length of the spectroscopic lens can be expressed by the following equation:

whereinP represents a pitch, and Z represents a length of the spectroscopical lens.

By adopting the scheme, the invention does not use the Greens lens with higher cost and larger size, and has the characteristics of simple structure, small volume and low cost.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic diagram of the graded-index fiber length and the wavelength of incident light according to the present invention;

FIG. 3 is a schematic diagram of the angle distance between the graded-index fiber and the beam splitting lens according to the present invention.

Description of reference numerals:

1. sealing the tube, 2, and injecting optical fiber; 3. an outgoing optical fiber; 4. a graded-index optical fiber; 41 graded index multimode fiber end bevels; 5. a spectroscopic lens; 51. an inclined plane of the spectroscopical lens; 6. a detector chip.

Detailed Description

In order to explain technical contents, structural features, and objects and effects of the present invention in detail, the following detailed description is given with reference to the accompanying drawings in conjunction with the embodiments.

Referring to fig. 1, in a compact optical signal monitoring and splitting detector according to the present invention, an input optical fiber 2 and an output optical fiber 3 as an input/output portion, a graded index multimode optical fiber 4 welded at the end portions of the input optical fiber 2 and the output optical fiber 3 by using an optical fiber fusion splicer, a splitting lens 5, and a detector chip 6 are sequentially disposed in a sealing tube 1. The input fiber 2 and the output fiber 3 are single mode fibers, and the input fiber 2 is used for inputting light beams. The beam splitting lens 5 is used for splitting an input beam from an input end into a transmitted beam and a reflected beam, the output end is used for outputting the reflected beam, and the detector chip 6 is used for converting the transmitted beam into an electric signal.

As shown in fig. 2, the length of the graded-index multimode fiber 4 is an odd multiple of the wavelength of the input beam 1/4 of the input fiber 2, and the graded-index multimode fiber 4 converts the input beam from a sine wave to a parallel beam.

As shown in FIGS. 1 and 3, the end of the GI multimode fiber 4 is polished at an angle θ₁The inclined surface 41 of the beam splitter lens 5 has a right trapezoid cross section, and the beam splitter lens is splitThe inclined surface 51 (i.e., the spectroscopic surface) of the lens 5 is parallel to the inclined surface of the end of the graded-index fiber.

Graded-index multimode fiber 4 capillary grinding angle theta₁The distance H between the centers of two optical fibers, the distance L between the centers of input light and output light on the inclined plane of the graded-index optical fiber, and the vertical distance S between the graded-index multimode optical fiber and the light splitting plane of the light splitting lens_ТThe relationship of (a) is as follows:

the relationship nsin theta between the grinding angle and the distance can be calculated according to the law of refraction, the law of reflection, a trigonometric function formula and a light path diagram shown in figure 3₁＝sinθ₂Wherein, theta₂Is the angle of incidence of the beam splitting surface of the beam splitting lens 5

H＝Lcosθ₁

S＝1/2Lcotθ₂(tanθ₂＝1/2L÷S_Т)

Therefore, when the GI multimode fiber 4 is ground at the capillary angle θ₁And the distance H between the centers of the two optical fibers is determined, the light splitting sheets with the same angle and the vertical distance between the two light splitting sheets can be determined according to the distance H

Vertical spacing S of 1/2Hsec theta₁cot[arcsin(nsinθ₁)]

(for parallel spacing S | ═ 1/2H sec2 θ₁cot[arcsin(nsinθ₁)])

At the time of actual production, theta₁At 6 deg., the GI multimode fibers used were thorlabs GIF625, 62.5/125, n was 1.491@1300nm, and the Numerical Aperture was 0.275 (i.e., 16 deg. at the maximum acceptable incident light angle and 0.275 deg. in sin16 deg.), the two fibers were placed close together with a center-to-center spacing H of 125um, when theta was measured₁When H is 125um at 6 °, θ₂＝8.97°，L＝125.69um，S_Т＝398.30um

The incident angle of the received light at the output end is theta₁+θ₂＝14.97°<16 deg. can be completely received

The refractive index of the GI multimode fibers 4 used varied with the radius as follows:

wherein n is₁Is the refractive index on the axis and,

for the gradient constant, r is the radial position (ranging from-D/2 to + D/2, where D is the diameter)

The relationship between the pitch of the GI multimode fiber 4 and the length of the spectroscopic lens can be expressed by the following equation:

where P denotes a pitch and Z denotes a length of the spectral lens 5.

When P takes 1/4 pitches, the proper length of the GI multimode fiber can be obtained to make the emergent light be collimated parallel light. The beam splitting lens splits the parallel light beam from the input end into a transmitted light beam and a reflected light beam. The transmitted light beam enters the detector and is converted into an electric signal, and the reflected light beam is output through the output end optical fiber.

The invention uses the optical fiber fusion splicer to fuse a section of multimode graded index optical fiber on the single mode optical fiber, sets the length of the multimode graded index optical fiber to be 1/4 pitch or odd times of the wavelength of the incident light, designs the light splitting LENS into a simple right-angle trapezoid, is easy to process, has lower cost, and compared with the prior art, does not need a large-size and high-cost G-LENS LENS (some need to add a focusing LENS) and does not need to process the light splitting LENS into a more complex structure (the angle calculation of a grinding angle sheet is more complex and the processing cost is higher) as in the background technology 2, therefore, the invention solves the technical problems in the prior art by using a small-size, simple structure and lower cost, which has obvious progress compared with the prior art.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. A compact optical signal monitoring spectrometer comprising: input/output portion, spectral lens, detector chip and seal the pipe, input/output portion is including input fiber and output fiber, its characterized in that: the input optical fiber and the output optical fiber are single mode optical fibers, a section of graded index multimode optical fiber is welded at the end parts of the input optical fiber and the output optical fiber, the length of the graded index multimode optical fiber is odd times of the wavelength of an input light beam 1/4 of the input optical fiber, and the end part of the graded index multimode optical fiber presents a grinding angle theta₁The section of the beam splitter lens is in a right trapezoid shape, the inclined plane of the beam splitter lens is parallel to the inclined plane of the end part of the graded-index multimode fiber, and the vertical distance S between the two inclined planes is 1/2Hsec theta₁cot[arcsin(nsinθ₁)]H is the distance between the centers of the two input and output optical fibers, and n is the refractive index; the relationship between the pitch of the GI multimode fiber and the length of the spectroscopic lens can be expressed by the following equation:

where P denotes a pitch and Z denotes a length of the spectroscopical lens.