CN102495477A - Optical mixer - Google Patents

Abstract

The invention belongs to the field of space coherent laser communication and relates to an optical mixer. The device consists of polarizers (3, 4, 8, 10, 12, 14), non-polarizing beam splitters (5, 7, 11), λ/4 wave plates (9, 13) and λ/2 wave plates (6) composition. The beam-splitting surface of the non-polarizing beamsplitter prism is coated with a semi-reflective and semi-transparent film, the λ/4 wave plate causes a 90-degree phase shift between the signal light and the local oscillator light, and the λ/2 wave plate makes the signal light and the local oscillator light Produces a 180 degree phase shift. After the signal light (1) and the local oscillator light (2) pass through the device, four coherent light outputs with relative phase differences of 90 degrees can be realized. The device has a compact structure, is simple and easy to implement, and can be applied to the coherent receiving field of free space laser communication.

Description

an optical mixer

technical field

The invention relates to an optical mixer, which is used to output four coherent lights with a relative phase difference of 90 degrees, and belongs to the technical field of free space laser communication.

Background technique

With the rapid development of the information age, space communication urgently needs high-speed data transmission. Compared with microwave communication, laser as a carrier has good communication potential. Compared with the currently widely used direct detection technology, coherent detection technology in the field of space laser communication has high sensitivity, long relay distance, good selectivity, large communication capacity, and more flexible application with multiple modulation methods. In order to achieve large-capacity, high-bit-rate, light-weight, and low-power spaceborne laser communication in free space, the application of coherent detection principles has become a research hotspot in free space laser communication. In coherent detection, the homodyne detection BPSK modulation method can theoretically obtain the highest detection sensitivity. The communication receiving end is composed of a local laser oscillator, a photoelectric receiver, a phase-locked loop, an optical mixer and a signal light receiving optical path. Among them, the optical hybrid linking the signal laser and the local oscillator laser to the photoelectric receiver is a key component of the coherent optical communication system. The 2x490-degree optical mixer mentioned in the literature R.Garreis, C.Zeiss, 90 opticalhybrid for coherent receiver, proc.SPIE, Vol.1522: 210-219, the principle is to use linear polarization and circular polarization to mix, using The combination of polarizing beam splitter or polarizing beam splitting prism and non-polarizing beam splitting prism requires a 90-degree phase difference between the transmitted light and reflected light on the beam-splitting surface of the non-polarizing beam-splitting prism, which has high requirements for the actual coating process. The present invention is different from it. The present invention adopts the mixing of linearly polarized light whose polarization directions are perpendicular to each other, and only adopts non-polarized beam splitting prisms. It is only required to coat the beam splitting surface with a semi-reflective and semi-transparent film, which is less demanding on the coating process and easier to implement. And the placement of the fast and slow axes of the wave plate is also different, and the principle of phase shift is also different. An optical mixer for spatial coherent laser communication (CN 102053381), which uses the mixing of two linearly polarized lights with the same polarization direction. Different from the present invention, the present invention adopts the mixing of two linearly polarized lights whose polarization directions are perpendicular to each other, and the optical principle is different. The device of the invention is compact in structure, simple and easy to implement, and can be applied to the coherent receiving field of free space laser communication.

Contents of the invention

The object of the present invention is to provide an optical mixer, which can coherently mix signal light and local oscillator light, and output four channels of coherent light with relative phase differences of 90 degrees.

The technical scheme of the present invention is: a kind of optical mixer, and its special feature is: a kind of optical mixer, and this device is made of polarizer (3), polarizer (4), non-polarization beam splitter prism (5), λ/2 wave plate (6), non-polarizing beam splitting prism (7), polarizing plate (8), λ/4 wave plate (9), polarizing plate (10), non-polarizing beam splitting prism (11), polarizing plate (12 ), λ/4 wave plate (13) and polarizer (14) form.

The light transmission axis direction of the polarizer (3) is parallel to the main section and perpendicular to the light propagation direction.

The light transmission axis direction of the polarizer (4) is perpendicular to the main section.

The fast axis direction of the above-mentioned λ/2 wave plate (6), λ/4 wave plate (9) and λ/4 wave plate (13) is parallel to the main section and perpendicular to the light propagation direction, and the slow axis direction is perpendicular to the main section.

The included angle between the light transmission axis of the above-mentioned polarizer (8), polarizer (10), polarizer (12) and polarizer (14) and the normal line of the main section is 45 degrees.

After the signal light (1) passes through the polarizer (3) and the local oscillator light (2) passes through the polarizer (4) and merges at the non-polarization beam splitter (5), the local oscillator light and the signal light are combined by the non-polarization beam splitter (5). After the light is mixed, it is divided into two paths, I and II. The I path is divided into two paths after passing through the non-polarizing beam splitter (7). One path is 0 after passing through the polarizer (8), and the other path passes through the λ/4 wave plate (9) and the polarizer. The rear phase of the sheet (10) is 90 degrees. The II road is divided into two roads after passing through the λ/2 wave plate (6) and the beam splitting prism (11), and the phase is 180 degrees after one road passes through the polarizing plate (12), and the other road passes through the λ/4 wave plate (13) and polarizing The rear phase of sheet (14) is 270 degrees.

Main technical problem and positive effect that the present invention can solve are:

1. It can realize coherent mixing of signal light and local oscillator light, and output four channels of coherent light with a phase shift of 90 degrees.

2. The principle scheme is simple and easy to implement, and the compact structure is conducive to the miniaturization design of the volume.

Description of drawings

Accompanying drawing is a kind of structure diagram of optical mixer;

Explanation of reference numerals: 1-signal light; 2-local oscillator light; 3-polarizing plate; 4-polarizing plate; 5-non-polarizing beam splitting prism; 6-λ/2 wave plate; Polarizing plate; 9-λ/4 wave plate; 10-polarizing plate; 11-non-polarizing beam splitter; 12-polarizing plate; 13-λ/4 wave plate; 14-polarizing plate.

Detailed ways

The present invention relates to a kind of optical mixer, and this device is made of polarizer (3), polarizer (4), non-polarization beam-splitting prism (5), λ/2 wave plate (6), non-polarization beam-splitter prism (7), A polarizer (8), a λ/4 wave plate (9), a polarizer (10), a non-polarizing beamsplitter (11), a polarizer (12), a λ/4 wave plate (13) and a polarizer (14) . The signal light (1) and the local oscillator light (2) pass through the polarizer (3) and the polarizer (4) respectively, then meet at the non-polarizing beam splitter (5), and then split into two paths after passing through the non-polarizing beam splitter (5) , one path of light is reflected by the non-polarizing prism (7), and then passes through the polarizer (8) to obtain coherent light with a phase of 0 degree. After being transmitted through the non-polarizing prism (7), coherent light with a relative phase of 90 degrees is obtained after passing through the polarizing plate (9) and the polarizing plate (10). The other light passes through the λ/2 wave plate (6), is transmitted through the non-polarizing beam splitting prism (11), and then passes through the polarizing plate (12) to obtain coherent light with a relative phase of 180 degrees. After being reflected by the non-polarizing dichroic prism (11), coherent light with a relative phase of 270 degrees is obtained after passing through the polarizing plate (13) and the polarizing plate (14).

Claims (5)

1. An optical mixer is characterized in that: by polarizer (3), polarizer (4), non-polarization beam splitter prism (5), λ/2 wave plate (6), non-polarization beam splitter prism (7) , polarizer (8), λ/4 wave plate (9), polarizer (10), non-polarizing beamsplitter prism (11), polarizer (12), λ/4 wave plate (13) and polarizer (14) constitute. 2. A kind of optical mixer according to claim 1, characterized in that: the signal light becomes linearly polarized light parallel to the main section and perpendicular to the direction of light propagation through the polarizer (3), and the local oscillator light passes through The polarizer (4) becomes linearly polarized light perpendicular to the main section. 3. A kind of optical mixer according to claim 1, is characterized in that: λ/4 wave plate (9), the fast axis direction of λ/4 wave plate (13) and λ/2 wave plate (6) Parallel to the main section and perpendicular to the direction of light propagation, the direction of the slow axis is perpendicular to the main section. 4. A kind of optical mixer according to claim 1, characterized in that: the light transmission axis and the main section of polarizer (8), polarizer (10), polarizer (12) and polarizer (14) The angle between the normals is 45 degrees. 5. According to claim 2, it is characterized in that: the light transmission axes of the polarizer (3) and the polarizer (4) can be interchanged.

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