Patent ID: 12253746

DETAILED DESCRIPTION

Embodiment 1

As shown in one ofFIGS.1to3, the present invention comprises a first polarizing beam splitter1, a half-wave plate2, a Faraday rotating plate3, a second polarizing beam splitter4, a quarter-wave plate5, and a pair of reflective plates6,7, wherein the first polarizing beam splitter1, the half-wave plate2, the Faraday rotating plate3, and the second polarizing beam splitter4are sequentially arranged, the quarter-wave plate5and the reflective plate6are sequentially attached to a side surface of the first polarizing beam splitter1adjacent to the half-wave plate2, and the reflective plate7is arranged on a side surface of the second polarizing beam splitter4adjacent to the Faraday rotating plate3; the first polarizing beam splitter1and the second polarizing beam splitter4are provided with polarizing splitting films11,41therein; preferably, the first polarizing beam splitter1and the second polarizing beam splitter4both comprise a pair of right-angled prisms, the inclined surfaces of the right-angled prisms are attached and fixed together, the attached and fixed inclined surfaces are provided with the polarizing splitting films11,41thereon, the polarizing splitting films on the first polarizing beam splitter1and the second polarizing beam splitter4are parallel to each other, a port1is formed on the end surface of the first polarizing beam splitter1opposite to the half-wave plate2, a port2is formed on the end surface thereof adjacent to the half-wave plate and opposite to the quarter-wave plate5, and a port3is formed on the end surface of the second polarizing beam splitter4opposite to the Faraday rotating plate3.

Furthermore, the optical axis of the half-wave plate2forms an angle of 22.5 degrees with the Faraday rotating plate3. The Faraday rotating plate3may be a magnetic Faraday rotating crystal plate or a Faraday rotating crystal plate with an externally applied magnetic field. In the case of a Faraday rotating crystal plate with an externally applied magnetic field, the peripheral side of the Faraday rotating plate is provided with a magnetic ring.

In addition, the first polarizing beam splitter1, the half-wave plate2, the Faraday rotating plate3, the second polarizing beam splitter4, the quarter-wave plate5, and the pair of reflective plates6,7are integrally fixed by means of optical bonding, diffusion bonding, or glue bonding.

Focusing onFIG.1andFIG.2, which are respectively schematic diagrams of a forward light path and a reflected light path of a signal light input through a port1, and when the signal light is input through an end surface of the first polarizing beam splitter1that is away from the half-wave plate2(i.e., the port1), the signal light is split by the polarizing splitting film11into a P light and an S light, wherein the P light passes through the polarizing splitting film11, then sequentially passes through the half-wave plate2and the Faraday rotating plate3, and then becomes the S light as its polarization state changes as a result of the nonreciprocal characteristic of the Faraday rotating plate3; the S light subsequently enters the second polarizing beam splitter4, is guided to the reflective plate7and is reflected by the reflective plate7back along the original path, then sequentially passes through the Faraday rotating plate3and the half-wave plate2, enters the first polarizing beam splitter1, is reflected by the polarizing splitting film11, and is output along the side of the first polarizing beam splitter1that is away from the quarter-wave plate5(i.e., the port2); after being reflected by the polarizing splitting film11to the side where the quarter-wave plate5is arranged and passing through the quarter-wave plate5, the S light is reflected by the reflective plate6back along the original path, and since the S light has passed through the quarter-wave plate5twice, the polarization state of the S light changes and the S light becomes the P light, which subsequently passes through the polarizing splitting film11and is output along the side of the first polarizing beam splitter1that is away from the quarter-wave plate5(i.e., output from the port2).

Focusing onFIG.3, which is a schematic diagram of a light path of a signal light input through a port3, and when the signal light is input through a side of the second polarizing beam splitter4that is away from the Faraday rotating plate3and forms a P light, the P light is guided by the second polarizing beam splitter4to sequentially pass through the Faraday rotating plate3and the half-wave plate2(due to the nonreciprocal characteristic of the Faraday rotating plate, the polarization state of the signal light in a direction from the port3to the port1does not change), then enters the first polarizing beam splitter1, and then passes through the polarizing splitting film11and is output from a side surface of the first polarizing beam splitter1that is away from the half-wave plate2(i.e., output from the port1).

In summary, the optical fiber arranged at the port1has the functions of transmitting and receiving, that is, bidirectional (BIDI).

The method for processing and manufacturing the structure in the present embodiment is briefly described as follows:1. manufacturing of the polarizing beam splitter (PBS) component: the component may be manufactured using a conventional optical cold processing plus coating, and the processing methods include, but are not limited to, glue bonding, optical bonding, and diffusion bonding. The PBS processing methods are relatively classic and will not be elaborated again herein;2. the wave plate component: this structure uses half-wave plates and ¼-wave plates, the optical axis thereof forms an angle of 22.5 degrees with the Faraday rotating plate, and the wave plate processing is mainly to control the thickness and optical axis direction thereof;3. the rotating component: a 45-degree Faraday rotating plate is used as the rotating component, including a magnetic type and a non-magnetic type (if the non-magnetic type is used, an additional small magnetic ring needs to be added), and a film needs to be coated on the glue of the Faraday rotating plate, so as to ensure good IL;4. the reflector component: the reflector component is relatively simple, which simply requires the coating of a reflective film with a corresponding wave hand on a piece of flat glass; and5. the several components listed above are attached together by means of glue bonding, optical bonding, or diffusion bonding to form a small free space circulator, which achieves transmitting and receiving functions in the vertical direction, has a smaller size, and realizes a more compact structure.

Embodiment 2

Referring toFIGS.4to6, the present embodiment is substantially the same as Embodiment 1 and differs in that the beam splitter is a birefringent crystal8, and the reflective plate7is arranged on a side surface of the birefringent crystal8opposite to the Faraday rotating plate3. Moreover, the reflective plate7partially covers the side surface of the birefringent crystal8opposite to the Faraday rotating plate3, the uncovered portion forms a port3for inputting a signal light, and the portion uncovered by the reflective plate may be provided with an optical lens or polarizing beam splitter9for guiding the P light in the signal light to be input into the birefringent crystal8. The structure of the present embodiment can similarly realize the functions of a BIDI free space circulator.

Focusing onFIG.4andFIG.5, which are respectively schematic diagrams of a forward light path and a reflected light path of a signal light input through a port1, the signal light is input through the port1and split by the polarizing splitting film11of the first polarizing beam splitter1into an S light and a P light, wherein the P light passes through the polarizing splitting film, and then becomes the S light after passing through a rotating assembly consisting of the half-wave plate2and the Faraday rotating plate3, wherein the S light is an O light in the birefringent crystal8with no birefringent phenomenon and no deviation of the light path. The light is incident perpendicularly onto the reflector7arranged at the rightmost side of the birefringent crystal8, and then returns along the original path. After the returned light passes through the rotating assembly that is nonreciprocal, its polarization state does not change, and it is still the S light, which returns into the first polarizing beam splitter1, is reflected by the polarizing splitting film11, and is then output from the port2. On the other hand, the other light, that is, the S light input through the port1and reflected by the polarizing splitting film11, is reflected to the side where the quarter-wave plate5is arranged and passes through the quarter-wave plate5, and then is reflected by the reflective plate6back along the original path. Since the S light has passed through the quarter-wave plate5twice, the polarization state of the S light changes and the S light becomes the P light, which subsequently passes through the polarizing splitting film11and is output along the side of the first polarizing beam splitter1that is away from the quarter-wave plate5(i.e., output from the port2), and forms a P+S combined light with the above-described returned S light.

Focusing onFIG.6, which is a schematic diagram of a light path of a signal light input through a port3, and when the signal light is input through the port3to form P light which goes into the birefringent crystal8, the light enters the previous original position after the walk-off effect by the birefringent crystal8(the P light is an E light in the birefringent crystal, and the light path will deviate). Since the Faraday rotating plate3is nonreciprocal and due to the transmission of the P light through the polarizing splitting film11, the P light smoothly passes all the way from the birefringent crystal8, the Faraday rotating plate3, and the half-wave plate2at the right side of the figure into the first polarizing beam splitter1at the left side, and is then output from the port1through the polarizing splitting film11. The light path process from the port3to the port1is described above, wherein the port1is equipped with the receiving and transmitting functions and realizes BIDI.

The method for processing the structure in the present embodiment is briefly described as follows:

1. the polarizing beam splitters, the wave plates, the rotating plate, and the reflectors are all similar to those in Embodiment 1 and will not be elaborated again;

2. the birefringent crystal component: YVO4 (with a relatively high birefringent coefficient) is usually selected, and the birefringent crystal is subject to a conventional optical cold processing method with the optical axis direction and crystal size being key indices, wherein the optical axis needs to be parallel to the paper surface, causing the S light to be an O light and the P light to be an E light, and the crystal needs to have such a size that the walk-off distance thereof can absolutely separate light spots. Specific calculations need to be performed for the above indices according to different applications and scenarios; and

3. the above components are attached together by means of glue bonding, optical bonding, or diffusion bonding to form a small free space circulator, which achieves transmitting and receiving functions in the vertical direction and has a small volume, but is slightly longer, in the length direction, than the structure A due to limitations by the walk-off crystal.

Embodiment 3

Referring toFIG.7, the present embodiment has substantially the same structure as that in Embodiment 1 and differs in that one side of an end surface of the second polarizing beam splitter4away from the reflective plate7is provided with a receiver configured to receive a portion of the P light reflected by the polarizing splitting film41(i.e., a port4is provided to receive a portion of the signal light input through the port3and reflected by the polarizing splitting film41). Although most of the P light transmits through the polarizing splitting film of the polarizing beam splitter, there is still about 3% of the P light that is reflected. Therefore, this portion of the reflected P light can be used as a monitoring light and received by using the receiver to monitor the power and stability of a laser inputting the signal light through the port3.

The first polarizing beam splitter1, the polarizing splitting film11, the half-wave plate2, the Faraday rotating plate3, the second polarizing beam splitter4, the polarizing splitting film41, the quarter-wave plate5, and the reflective plates6,7in the present embodiment are all the same as those in Embodiment 1, and the light paths thereof are also the same. Therefore, they will not be elaborated again.

Embodiment 4

Referring toFIG.8, the present embodiment has substantially the same structure as that in Embodiment 2 and differs in that one side of an end surface of the input port of the birefringent crystal8away from the reflective plate7is provided with a receiver configured to receive a portion of the P light reflected by the polarizing beam splitter9(i.e., a port4is provided to receive a portion of the signal light input through the port3and reflected by the polarizing beam splitter9). Although most of the P light transmits through the polarizing splitting film of the polarizing beam splitter9, there is still about 3% of the P light that is reflected. Therefore, this portion of the reflected P light can be used as a monitoring light and received by using the receiver to monitor the power and stability of a laser inputting the signal light through the port3.

The first polarizing beam splitter1, the polarizing splitting film11, the half-wave plate2, the Faraday rotating plate3, the birefringent crystal8, the quarter-wave plate5, and the reflective plates6,7in the present embodiment are all the same as those in Embodiment 2, and the light paths thereof are also the same (wherein the light path of the signal light input through the port3is slightly deviated). Therefore, they will not be elaborated again.

Embodiment 5

In addition to Insertion Loss (IL) and isolation (ISO), Return Loss (RL) is also a key factor for a free space circulator. The present embodiment provides an extension to the implemented structures in Embodiments 1 through 4, wherein a wedge may be added into the above structures, or the right-angled surface of PBS may be processed into an inclined surface to increase RL. SeeFIG.9for details.FIG.9is an extension to the structure in Embodiment 1. The first polarizing beam splitter1, the polarizing splitting film11, the half-wave plate2, the Faraday rotating plate3, the second polarizing beam splitter4, the polarizing splitting film41, the quarter-wave plate5, and the reflective plates6,7illustrated in this structure are all the same as those in Embodiment 1, and the light paths thereof are also the same. Therefore, they will not be elaborated again.

In summary, with regard to the concept of the solutions of the present invention, Embodiments 1 through 5 respectively propose a general structure of receiving and transmitting in the vertical direction, a structure of receiving and transmitting in the vertical direction and having a birefringent crystal, a structure of receiving and transmitting in the lateral direction, and a series of derived structures with a monitoring PD, as well as corresponding sub-types of structures proposed for improving RL. To those of ordinary skills in the art, any equivalent changes, modifications, substitutions, and variations made according to the teaching of the present invention and following the scope of the patent applied for the present invention without departing from the principle and spirit of the present invention shall fall within the scope of the present invention.