CN210401741U - Directional filter - Google Patents

Abstract

The utility model relates to the field of optical fiber communication, in particular to a directional filter, which comprises a beam splitter, a rotator and a filter plate; the end surface inclination angle of the optical splitter is designed, so that incident light and emergent light are symmetrical about an axis, and packaging is facilitated; the rotator adopts a non-reciprocal optical element and has different changes on the polarization states of the forward light and the reverse light; the filtering plates are arranged adjacently and respectively filter the uplink light path and the downlink light path. Directional filter, it adopts non-reciprocal material for light signal unidirectional transmission. The transmitting port can not receive the optical signal with the self wavelength, and the echo interference to the system is reduced.

Description

Directional filter

Technical Field

The utility model relates to an optical fiber communication field specifically is a directional filter.

Background

A directional filter, typically has two ports, one of which transmits a λ 1 signal while receiving a λ 2 signal, and the other of which, in reverse, transmits a λ 2 signal while receiving a λ 1 signal. The directional filter has both the wavelength characteristic of the filter and the directional characteristic of the coupler. The optical fiber is mainly used for simultaneously receiving and transmitting optical signals in two directions by one optical fiber. The transmission capability of the optical fiber is doubled, and the optical fiber resource is saved.

The mainstream solution in the market is single-fiber bidirectional, and these solutions adopt reciprocal materials, and crosstalk is generated due to material interface reflection. For example, when a port transmits a λ 1 signal, some nodes of the line may reflect a portion of the light of the λ 1 signal, thereby causing interference with the laser.

Disclosure of Invention

An object of the utility model is to overcome above-mentioned defect, provide a directional filter, and then avoid the interference phenomenon.

In order to achieve the above object, the present invention is realized as follows:

in order to achieve the above object, the present invention is realized as follows:

a directional filter comprises a beam splitter, a rotator and a filter plate; the end surface inclination angle of the optical splitter is designed, so that incident light and emergent light are symmetrical about an axis, and packaging is facilitated; the rotator adopts a non-reciprocal optical element and has different changes on the polarization states of the forward light and the reverse light; the filtering plates are arranged adjacently and respectively filter the uplink light path and the downlink light path.

Directional filter, it adopts non-reciprocal material for light signal unidirectional transmission. The transmitting port can not receive the optical signal with the self wavelength, and the echo interference to the system is reduced.

Drawings

FIG. 1 is a schematic diagram of the slope angle and the optical axis angle of the optical splitter and the optical path.

Fig. 2a is a schematic diagram of the change of polarization state of light when a rotator is applied to forward light.

Fig. 2b is a schematic diagram of the change of polarization state of light by the rotator acting on the reversed light.

Fig. 3 is a three-dimensional schematic diagram of an ascending light path and a projection diagram of a light polarization state in an xy plane.

Fig. 4 is a three-dimensional schematic diagram of the down light path and a projection view of the light polarization state in the xy plane.

Detailed Description

A directional filter comprises a beam splitter, a rotator and a filter plate;

as shown in FIG. 1, the front and back end faces of the beam splitter are inclined planes, and the normal of the inclined planes is in the same plane with the optical axis. The inclined plane inclination angle is 5.7 degrees, and the optical axis angle is 45 degrees, so that incident light and emergent light are symmetrical about an axis, and coaxial packaging is facilitated.

The optical rotator is composed of a pair of half-wave plates and a Faraday optical rotation plate, wherein the Faraday optical rotation plate is a non-reciprocal material.

As shown in fig. 2a, two beams of forward linearly polarized light with orthogonal polarization directions pass through a pair of half-wave plate and faraday optical rotation plate successively, and then become two beams of linearly polarized light with vertical polarization directions.

As shown in fig. 2b, two opposite linearly polarized lights with horizontal polarization directions pass through the faraday rotation plate and the pair of half-wave plates in sequence, and then become two linearly polarized lights with orthogonal polarization directions.

Fig. 3 is a three-dimensional schematic diagram of an ascending light path and a projection diagram of a light polarization state in an xy plane.

Incident light 1 carries any polarization component, travels along the z-axis, and is incident on a beam splitter 2.

The normal line of the end face of the beam splitter 2 and the optical axis are both in the xz plane, and the incident light 1 is split into two linearly polarized light beams 3 and 4 along the x direction, the polarization directions of the two linearly polarized light beams are orthogonal, and the two linearly polarized light beams enter the optical rotator 5.

And an optical rotator 5 including a pair of half-wave plates and a Faraday rotator. After passing through the optical rotator 5, the light beams 3 and 4 have the same polarization direction and are incident on the beam splitter 6.

The normal to the end face of the beam splitter 6 and the optical axis are in the yz plane, the light beams 3 and 4 follow ordinary refraction, and the transmission locus is displaced △ in the-y direction and enters the filter 7.

Between the beam splitters 6 and 8, filters 7 and 15 are adjacently arranged in the y direction.

The filter 7 is disposed on the upstream optical path and filters the upstream light. After passing through the filter 7, the light beams 3 and 4 contain only specific wavelength components and enter the beam splitter 8.

The beam splitter 8 has the same tilt and optical axis orientation as the beam splitter 6 the beams 3 and 4 follow extraordinary refraction and the propagation path is shifted △ back in the y-direction to the optical rotator 9.

The optical rotator 9 is the same as the optical rotator 5, and is also composed of a pair of half-wave plates and a faraday plate. After passing through the optical rotator 11, the light beams 3 and 4 have orthogonal polarization directions and enter the optical splitter 10.

The beam splitter 10 has the same tilt angle and the same optical axis orientation as the beam splitter 2, and the beams 3 and 4 are combined into an outgoing beam 11 in the x direction and emitted from the beam splitter 10. The outgoing light 11 carries an arbitrary polarization component, but contains only a wavelength component corresponding to the filter 7.

Fig. 4 is a three-dimensional schematic diagram of the down light path and a projection view of the light polarization state in the xy plane.

The downlink optical path is transmitted along the reverse direction of the uplink optical path. The incident light 12 is split into two linearly polarized light beams 13 and 14 in the x-direction.

The main characteristic of the downstream optical path is that the optical path is displaced △ along the y direction between the optical splitter 6 and the optical splitter 8, the filter 15 is arranged on the downstream optical path to filter the downstream light, and the emergent light 16 only contains the wavelength component corresponding to the filter 15.

Claims (1)

1. A directional filter, characterized by: comprises a light splitter, a rotator and a filter plate; the end surface inclination angle of the optical splitter is designed, so that incident light and emergent light are symmetrical about an axis, and packaging is facilitated; the rotator adopts a non-reciprocal optical element and has different changes on the polarization states of the forward light and the reverse light; the filtering plates are arranged adjacently and respectively filter the uplink light path and the downlink light path.

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