CN1419143A - Optical path mixing device - Google Patents

Abstract

The optical path hybrid device belongs to the optical device in the field of optical communication, and specifically relates to an optical path integrated device, which can integrate three functions of a wavelength division multiplexer, an optical isolator and an optical coupler into one device, and is used in an optical fiber amplifier. In the transmission direction of the optical path, the device includes the first double-fiber collimator with a WDM filter attached to its output end face, and a wedge-type isolator composed of two birefringent crystal wedges and a Faraday-rotation optical crystal. The cross-section is six The beam-splitting prism of the polygonal shape and the second double-fiber collimator, the wedge-type isolator and the beam-splitting prism can be sandwiched between two glass plates, and together they are packed into a magnetic ring made of permanent magnet material. The three functions of the device are integrated in one device, which can reduce the amount of collimators and packaging accessories, reduce the cost, and at the same time have a smaller volume.

Description

optical path hybrid device

technical field

The invention belongs to optical devices in the technical field of optical communication, and in particular relates to an optical path integrated device.

Background technique

In optical fiber communication systems, in order to increase the transmission distance of optical signals, a large number of optical fiber amplifiers are needed, such as Erbium-doped fiber amplifiers (EDFA), and in optical fiber amplifiers, wavelength division multiplexers (WDM), optical Optical passive devices such as isolators (ISO) and split optical couplers (TAP). The wavelength division multiplexer couples the pump light and the signal light into the optical fiber of the amplifier; the optical isolator can prevent the influence of reflected light on the laser; the optical splitter takes a part of the pre-amplified or post-amplified signal for monitoring It is used to control the gain or display the amplified optical power of the signal.

Erbium-doped fiber amplifiers can be pumped forward, backward or bidirectionally according to the actual application. The pump light of the forward pump and the signal light are transmitted in the same direction in the erbium-doped fiber, and the pump light of the backward pump is the same as the signal light. The transmission direction of light in the erbium-doped fiber is opposite, and bidirectional pumping uses two pumping lights whose transmission directions are the same and opposite to those of the signal light for pumping. In order to reduce the volume and reduce the cost, the patent US5082343 proposes a scheme for making a wavelength division multiplexer and isolator hybrid device. There are two implementation methods, which can be used in forward and backward pumped erbium-doped fiber amplifiers respectively; Patent US5555330 proposes a solution that can integrate the four functions of wavelength division multiplexer, optical isolator, optical coupler and monitoring light detector into one device. There are also two implementation methods, which can be used for forward and backward respectively. In the pumped erbium-doped fiber amplifier; the patent US6181850 B1 proposes another solution, which has multiple implementation methods and can integrate two, three or four functions respectively, and is used for forward and backward pumped erbium-doped fiber amplifiers. in the fiber amplifier. Patent US5082343 only integrates two functions, and the other two patents can integrate more functions, but they are more complicated and larger in size.

Contents of the invention

The invention provides an optical path hybrid device, which can integrate three functions of a wavelength division multiplexer, an optical isolator and an optical coupler into one device, and is used in a backward pumped erbium-doped fiber amplifier. Small, low-cost new solution.

An optical path hybrid device of the present invention comprises a first double optical fiber collimator with a WDM filter attached to its output end face in the direction of optical path transmission, and a wedge composed of two birefringent crystal wedges and a Faraday rotation optical crystal Type isolator and the second double-fiber collimator, it is characterized in that: (1) between wedge-type isolator and the second double-fiber collimator, be provided with the dichroic prism that section is hexagon; (2) described Corresponding anti-reflection coatings, anti-reflection coatings and partial reflection coatings are coated on each surface of the dichroic prism.

The optical path mixing device is further characterized in that the optical axes of the two birefringent crystal wedges forming the wedge type isolator form an included angle of 45°, and the rotation angle of the Faraday rotation crystal to the polarization plane of polarized light is 45°, each The light-transmitting surface of the component is coated with an anti-reflection film with the signal light wavelength as the center wavelength.

In the optical path hybrid device, the end face of the pigtail connected to the pumping light source of the first double-fiber collimator can be coated with an anti-reflection coating with the wavelength of the pump light as the center wavelength, and the other end face of the pigtail and the two collimating lenses The first end face can be coated with an anti-reflection film with the signal light wavelength as the center wavelength, and the collimating lens of the second double fiber collimator and the end faces of the two pigtails can be coated with an anti-reflection film with the signal light wavelength as the center wavelength.

In the optical path mixing device, two wedge-type isolators can be placed in series in the optical path.

In the optical path mixing device, the wedge-type isolator and the dichroic prism can also be sandwiched between two glass sheets, and they can be packed together into a magnetic ring made of permanent magnet material.

Features of the present invention are: 1. A beam splitting prism has been designed to realize the light splitting function, which can divide the signal light into two beams of light with a power ratio of 99:1, and the angle between the two beams of light is 3.70 °, and the second double optical fiber The two output beams of the collimator have the same angle (Cross Angle), so they can be well coupled into the two pigtails of the dual fiber collimator; 2. The splitter prism and the isolator unit are clamped together in two In the middle of the glass sheet, and considering the matching of the beam lateral offset (Offset) in the isolator and the optical path in the splitter prism, assembly and debugging are more convenient; 3. The three functions are integrated in one device, which can reduce collimators and other packaging accessories The dosage can reduce the cost, and at the same time, the volume can be smaller, and the outer diameter is the same as that of the current commercial online optical isolator.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the present invention.

Fig. 2 shows an external connection mode of the present invention.

Fig. 3 is a schematic diagram of the first dual-fiber collimator.

Figure 4 is a schematic side view of the isolator and beam splitter package.

Fig. 5A shows the propagation trajectory of forward light in the isolator, and Fig. 5B shows the propagation trajectory of reverse light.

Fig. 6 is a schematic diagram of an optical path of an isolator and a beam splitting prism.

Fig. 7 is a schematic diagram of the second double-fiber collimator.

FIG. 8A shows the polarization state change process of the forward light in the isolator, and FIG. 8B shows the polarization state change process of the reverse light.

Figure 9 shows the angle and coating design of the splitter prism.

Detailed ways

In conjunction with Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 6A, Fig. 6B, Fig. 9, the optical path hybrid device includes the first double fiber collimator 2A, WDM filter 3, a Wedge type isolator unit (wedge angle sheet 4A, 4B, Faraday rotation optical crystal 5), dichroic prism 6, the second double-fiber collimator 2B, the WDM filter is pasted on the end face of the self-focusing lens (GRIN-LENS) of the first double-fiber collimator, and the reflection The pump light P allows the signal light S to pass through; the isolator unit and the splitter prism are clamped together between two glass plates 8A and 8B, and are installed together in the magnetic ring 7; when in use, the pigtail 1A is connected to the erbium-doped optical fiber , 1B is connected to the pump light source, 1C is connected to the communication optical fiber, and 1D is connected to the detector, as shown in Figure 2. The pump light is input from the pigtail 1B, after being collimated by the collimator 2A, it is reflected by the WDM filter 3 pasted on the end surface of its self-focusing lens, enters the collimator 2A again and is output from the pigtail 1A, and enters the erbium-doped Optical fiber; the signal light amplified in the erbium-doped optical fiber is input from the pigtail 1A, collimated by the collimator 2A, passes through the WDM filter 3, and enters the isolator unit, as shown in FIG. 3 . In the isolator unit, the signal light is divided into o light and e light to propagate. At the exit position, the two beams of light are separated by a small distance (Walk-off); in addition, the two beams of light have some lateral offset (Offset), The outgoing direction is the same as the incoming direction, as shown in Fig. 5A. The lateral offset of the signal light in the isolator unit matches the design of the splitter prism 6, so that the signal light is incident on the center of the incident surface of the splitter prism, and after passing through the prism, it is divided into a power ratio of 99:1 (design as required , can be divided into other proportions), two beams of light with an included angle of 3.70° are respectively coupled into two pigtail fibers 1C and 1D of the collimator 2B, as shown in FIGS. 6 and 7 . 99% of the signal light is output from the pigtail 1C, enters the communication fiber, and continues to be transmitted; 1% of the signal light is output from the pigtail 1D, and sent to the detector for displaying the amplified signal light power and gain control. The reverse light from the pigtail 1C or 1D first passes through the splitter prism, but when passing through the isolator unit, it will be deviated from the original propagation direction and thus isolated, as shown in Figure 5B.

In order to make the pump light input from the pigtail 1B of the collimator 2A be output from the pigtail 1A after being reflected by the WDM filter 3, the input double fiber collimator should adopt a self-focusing lens with a pitch of 0.25; in order to reduce Insertion loss, output dual-fiber collimator 2B should consider the working distance, using a 0.23-pitch self-focusing lens. The isolator unit is a polarization-independent Wedge type, consisting of two birefringent crystal wedges 4A and 4B, and a Faraday rotation optical crystal 5 sandwiched therein. The optical axes of the two wedges form an angle of 45°, and the Faraday rotation The rotation angle of the crystal to the polarization plane of linearly polarized light is also 45°, as shown in Figure 8A and Figure 8B; in order to obtain higher isolation and wider bandwidth, the isolator unit can also use two stages. The design of the dichroic prism is shown in Figure 9. Each light-transmitting surface is coated with an anti-reflection coating, an anti-reflection coating, and a 1% partial reflection film; the 1% partial reflection film is replaced by other ratios, and different proportions can be separated. Signal light; the angle θ is designed according to the angle between the two output beams of the dual-fiber collimator 2B, that is, the Cross Angle, where the Cross Angle and θ are both 3.70°, so the angle between the two separated beams of light is also 3.70°; One of the characteristics of the beam splitting prism is that due to processing and assembly errors, there is a certain error in the incident angle of the signal light on the beam splitting prism, but the angle between the two separated beams of light changes very little, still about 3.70°, which does not affect the connection with the double beam. Coupling between fiber collimators 2B.

Claims (9)

1. light path hybrid device, comprise first double-fiber collimator that is pasted with the WDM filter plate on its output end face successively in the optic path direction, by two birefringece crystal angle of wedge sheets and a wedge type isolator and second double-fiber collimator that the Faraday crystal is formed, it is characterized in that:

(1) being provided with the cross section between the wedge type isolator and second double-fiber collimator is hexagonal Amici prism;

(2) on each face of described Amici prism the plating corresponding anti-reflection film, increase anti-film and partial reflection film.

2. light path hybrid device as claimed in claim 1, the optical axis angle at 45, the Faraday crystal that it is characterized in that forming two birefringece crystal angle of wedge sheets of wedge type isolator are 45 ° to the rotation angle of polarized light plane of polarization, and the logical light face plating of each element is the anti-reflection film of centre wavelength with the signal light wavelength.

3. light path hybrid device as claimed in claim 1 or 2, the tail optical fiber end face plating that it is characterized in that described first double-fiber collimator connection pump light source is the anti-reflection film of centre wavelength with the pump light wavelength, two end face platings of another root tail optical fiber end face and collimation lens are the anti-reflection film of centre wavelength with the signal light wavelength, and it is the anti-reflection film of centre wavelength that the end face of the collimation lens of described second double-fiber collimator and two tail optical fibers all plates with the signal light wavelength.

4. light path hybrid device as claimed in claim 1 or 2 is characterized in that described wedge type isolator can be that two series connection are placed in the light path.

5. light path mixer as claimed in claim 3 is characterized in that described wedge type isolator can be that two series connection are placed in the light path.

6. light path hybrid device as claimed in claim 1 or 2 is characterized in that described wedge type isolator and Amici prism are installed between two glass sheet together, and in the magnet ring made of the permanent magnet material of packing into together.

7. light path hybrid device as claimed in claim 3 is characterized in that described wedge type isolator and Amici prism are installed between two glass sheet together, and in the magnet ring made of the permanent magnet material of packing into together.

8. light path hybrid device as claimed in claim 4 is characterized in that described wedge type isolator and Amici prism are installed between two glass sheet together, and in the magnet ring made of the permanent magnet material of packing into together.

9. light path hybrid device as claimed in claim 5 is characterized in that described wedge type isolator and Amici prism are installed between two glass sheet together, and in the magnet ring made of the permanent magnet material of packing into together.

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