JPS59219706A - Module of plane of polarization maintaining optical fiber and laser diode - Google Patents

Abstract

PURPOSE:To separate and remove an unnecessary polarized light component and to improve the efficiency of optical coupling, by constituting and arranging a laser diode, spherical lens, Rochon prism for separating polarized light, and plane of polarization maintaining optical fiber in the described order, so that a specific condition is satisfied. CONSTITUTION:A spherical lens 3 and Rochon prism for separating polarized light 4 are arranged as shown in the figure between a laser diode 1 and plane of polarization maintaining optical fiber 2 along the central axis of a module. The laser diode 1, optical fiber 2, and spherical lens 3 are constituted and arranged so that they satisfy equations I and II simultaneously. Therefore, a high efficiency of optical coupling is obtained and a laser light O from the laser diode 1 is separated to each polarized component O1 and O2 and only one component O1 is made incident to the optical fiber 2. The other component O2 is not made incident to the optical fiber 2 and removed as an unncessary polarized light component.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to optical transmission technology, and in particular to a polarization-maintaining optical fiber laser diode monoyl (hereinafter also simply referred to as one optical coupling module J) that couples a polarization-maintaining optical fiber and a laser diode. (abbreviated)).

Background of the Technology The progress of optical transmission technology using optical fibers is remarkable, and it has already reached the level of practical use in the telecommunications sector, and its practical application in planning and many other fields is also actively progressing.

However, conventional optical fiber transmission technology generally involves converting the information signal and the process to be measured from 1 to a light amplitude 11'i+c, that is, a light intensity signal, and transmitting the converted signal through the original fiber. In view of this, in recent years there has been much research into the practical application of so-called coherence optical transmission, in which information and the process to be measured are transmitted on the optical phase 1 frequency θ, on the polarization plane. Polarization-maintaining optical fibers that preserve and stably transmit and transmit phase inertia are attracting attention, and active development is underway.

Currently, the most promising light source for such coherent light transmission is a semiconductor radar such as a radar diode. Various types of Radede diodes have been developed, but from the viewpoint of stabilizing the transverse mode of the resonator, the so-called striped structure in which the C light emitting region is in the form of a band is most suitable.
i am doing In a laser diode, it is ideal for the Raded light to have a single polarization mode, so-called completely linear polarization, but in reality, due to the asymmetry of the Raded structure, perfect linear polarization cannot be obtained; for example, X polarization and The polarized waves are generated at a ratio of about 20 dB. Therefore, for example, if it is desired to use only the X-polarized wave as a signal carrier, the X-polarized wave becomes noise and must be removed before the laser beam enters the optical fiber.

On the other hand, in a polarization maintaining optical fiber V, if the optical fiber is uniform in the longitudinal direction, the polarization and the position 4Ll! fr'i
However, it is practically difficult to make such a perfect optical fiber, and it is prone to disturbances (bending, bending, etc.).
The state of polarization can easily change depending on the screws (4+) and the small parts of the S structure (fluctuations at the boundaries between the core, the center, and the center). Therefore, it is desirable to extract only safe polarized components from the light emitted from optical fibers.

Advancement technology and problems Conventional Yuzu l'A as an optical coupling module as mentioned above.
construction is proposed.

An example is the absence of a single ball lens between the laser diode and the optical fiber.

However, with this structure, it is not possible to separate and remove unnecessary polarized components as described above.

Another example is to arrange a ball lens for a laser diode and a ball lens for an optical fiber along the optical axis between the laser diode and the original fiber. In this method, a polarization separation plate such as a Rochon grism is further placed between the Shira-gai lenses. In this structure, the polarization separation plate separates the X polarization and the Y polarization so that only the necessary polarization components enter the optical fiber, that is, the unnecessary polarization components are removed. However, on the other hand, there is a drawback that noise and optical phase noise are generated due to deterioration of the degree of polarization separation due to multiple reflections and diffused reflections on the surface of the Rochon prism and the end face of the optical fiber.

Yet another example is one in which the optical fiber is arranged at an angle with respect to the mechanical central axis in the structure of the first example. However, this structure has the drawback that the module has a bent shape and optical coupling loss is large.

Purpose of the Invention The present invention is based on the above-mentioned prior art, and is capable of separating and removing unnecessary polarization components from the incident Raded light from the laser diode to the optical fiber in optical coupling between the polarization maintaining optical fiber and the Raded diode, Moreover, it is an object of the present invention to provide a polarization-maintaining optical fiber diode module with high optical coupling efficiency.

The present invention also provides a polarization-maintaining optical fiber laser diode monole that can separate the returned light from a 1/in. The purpose is to

Structure of the Invention The polarization-maintaining optical fiber laser diode module according to the present invention generally comprises a laser diode, a ball lens, a (J+II optical 9-separation Lon-Yon prism, and a polarization-maintaining optical fiber) in that order. 1, and arranged so that the center 1111 gland of the optical fiber and the ball lens coincides with the Ziehl mechanical central axis, and the optical axis of the Rede diode deviates from the mechanical central axis, and the Rede diode, The optical surfaces of the Rochon prism and the optical fiber are all configured to form a jet angle with respect to a plane perpendicular to the mechanical center axis, and the formula is as follows: tl: Distance between the center of the Raded diode and the ball lens t2: Sphere Distance f between the center of the lens and the optical fiber: Focal length of the spherical lens ωLD' Gaussian beam spot size of the radar diode ωF: The Gaussian beam spot size of the optical fiber was made to add 111 at the same time #tI) It is something.

Another configuration of the present invention is that, in addition to the above configuration, a -7 mirror is arranged between the radar diode and the ball lens to reflect the light emitted from the optical fiber. It is.

Embodiments of the Invention Below, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows the structure of an embodiment of an optical coupling module between a polarization maintaining optical fiber and a radar diode according to the present invention. In the figure, matrix 1 indicates a laser diode, and numeral 2 indicates a polarization-maintaining optical fiber (hereinafter abbreviated simply as 1 optical fiber). A ball lens 3 and a Rochon prism 4 for polarization separation are arranged between the radar diode 1 and the optical fiber 2 in the order shown.

Further, reference numeral 5 indicates the mechanical center axis of the module,
Optical fiber? The optical axes of ball lens 2 and ball lens 30 coincide with this mechanical center axis. However, the optical axis Fi of the Rede diode 1 is deviated from the radical center ii1+gland 5. The optical surface 1as of the laser diode 1, the optical surface 2a1 of the optical fiber 2, and the optical surfaces 4m and 4b of the Rochon prism 4 are all at inclination angles of 01 and 'I! It has yθ3. And among the Mosor elements mentioned above, there is 1 laser diode, 9 Phino' 2,! The lenses 3 are arranged in a 44'4 configuration so as to simultaneously satisfy the following equations (1) and (2).

(uL, l-s: Distance between the laser diode and the center of the spherical lens t2 Distance between the center of the two-sphere lens and the optical fiber f: Focal length of the spherical lens ωLD' Gaussian beam spot size of the laser diode ωF: Gaussian of the optical fiber Beam spot size f above is determined from the following equation.

However, n: refractive index of the ball lens Radius of R1 sphere lens Further, the above ωLD rω, F can be obtained from the following equation.

ω, 2nd and 2nd i4- However, ωLD1#ωLD2 are the semi-major axis and semi-minor axis of the beam spot of the radar diode 1, respectively, as shown in FIG. 2, and ωF1. ω1. , 2 are the major axis and minor axis of the beam spot of the optical fiber 2, respectively, as shown in FIG. Generally, ωLD=4μm, ω,=
5μmn8 degrees.

Next, as shown in FIG.
2) The two prisms 6 and 7 made from
At A! i! It consists of D. One prism 6 has a crystal axis 6 parallel to the mechanical central axis 5 (Fig. 1).
It has a. The other prism 7 has a crystal axis 7a perpendicular to the crystal axis 6a. However, the crystal axes 6a and 7a are both parallel to the mechanical center axis 5 and parallel to the plane 9 perpendicular to the plane of the drawing. Upper and lower surfaces 4c of the lotion prism 4,
It is parallel to the mechanical central axis 5 of the 4dFi machine, and the front and rear optical surfaces 4a, 4b have an inclination angle θ3 with respect to a plane perpendicular to the mechanical central axis 5, as described above.

Further, the joint surface 8 of the frame 6.7 similarly has an inclination angle θ4 with respect to a plane perpendicular 1a to the mechanical central axis 5.

The Rochon prism 4 exhibits different refractive indexes for normal light parallel to the crystal axis of the prism and extraordinary light intersecting the crystal axis, and serves to separate incident light into polarized components. That is, as shown in FIG. 1, the laser beam 0 from the radar diode 1 is separated into polarization components 01e02 by the Rochon prism 4, and one polarization component 0
Further, the polarized wave component 02 of the external force that is incident on the injured fiber 2 is not input into the optical fiber 2 and is removed as an unnecessary polarized wave component. Incidentally, which polarization component is to be used or not can be arbitrarily selected by shifting the position of the optical fiber 2 so that only the desired single polarization component enters the optical fiber 2. 4).

As described above, in the optical coupling module of the present invention, the laser light from the laser diode is separated into polarization components by the Rochon prism before entering the original fiber, and the unnecessary polarization component power "F" is separated. , and achieves low-noise transmission of only a single polarized component with 0'J capability.Also, by configuring each module element to satisfy equations (1) and (2) above, high optical coupling efficiency is achieved. Furthermore, since the optical surface of the valley seven-nor element has an angle of inclination with respect to the plane perpendicular to the mechanical center axis of the module, the light beam necessarily makes an angle with respect to the normal to the mechanical axis of the module. Since the light is incident incidentally, noise caused by deterioration of the degree of polarization separation due to multiple reflections and diffused reflection, as well as optical number card noise, which occur in the past, can be prevented.

In the first embodiment, the inclination angle of the optical surface of each module element is θ1=3° to lO°, and θ2=24° to 6°.

θ3=0.6° to 5° is appropriate. Regarding the lotion prism 4, the thickness is t-1, s rtnn N
Length of vertical and horizontal sides h=3, θ3=0.67', θ
An angle of about 4-14 degrees is suitable. In addition, in the lotion prism -1, t'c science 114a, 4bO parallelism is 171000, the perpendicularity of the crystal axes 6a, 7a of the Norism 6, 7 is 1/1000, -1 = parallelism of the lower surfaces 4c, 4d and the crystal axis plane 9 It is desirable to have an accuracy of 17100i degrees.

Next, FIG. 5 shows a second embodiment of the optical coupling module according to the present invention. This embodiment has the same basic configuration as the first embodiment, but a half mirror 1o is added between the radar diode 1 and the ball lens 3. While the first embodiment is applicable only to transmission, the second embodiment is intended to be applied, for example, to the transmitting/receiving part when transmitting and receiving using the same optical fiber or to the input/output part of an optical fiber gyro. This is what I did. In other words, in the case of bidirectional transmission using the same optical fiber, even if unnecessary polarization components are removed from the light incident on the optical fiber, disturbances to the optical fiber and non-uniformity of the optical fiber structure may cause interference during optical fiber transmission as described above. Unnecessary polarization components are generated. Therefore, it is desirable that the receiving section separates the light emitted from the optical fiber into polarization components so that only the necessary polarization components can be received. .

In the second embodiment, the output light beam 1 from the optical fiber 2 is
is separated into two polarization components M1 and M2 by the polarization separation effect of the Rochon prism 4 as described above. These separated '1 Jin wave components Ml.

A portion of the light is reflected by the MIIU half mirror 10 and output to the side of the module. Therefore, by arranging the values of the respective output position photodetectors DI and D2, it is possible to detect the polarized components of Ijj.

Next, FIGS. 6, 7, and 81 schematically show specific examples of the optical coupling module of the present invention. In FIG. 6, the reference numeral 2o indicates an L-shaped metal fitting made of a material such as Super Invar, and the laser diode l and lotion prism 4 (omitted in H+61x+) are metal fittings 2.
01C For example, 1 haj of engraving is added by 1. Further, the optical fiber 2 is held by a core 21, and the core 21 is held by a metal fitting 2o using two rust-shaped core holders 22 as shown in FIG.
In order to keep it in place. Furthermore, the ball lens 3 is the eighth
As shown in the figure, attach the n-riff rust type lens holder 23 to 2.
(It is held in position by the metal fitting 20 using II\iI.

In FIG. 8, (A) is a plan view of the lens holder 23, and (→ and () are both end views thereof.

The above structure is simple and provides high assembly accuracy.
It is possible to realize highly reliable optical coupling monolayer.

Effects of the Invention As described above, according to the present invention, it is possible to separate and remove unnecessary polarization components from the laser light incident on the optical fiber from the laser diode in optical coupling between the polarization maintaining optical fiber and the laser diode. Moreover, a polarization-maintaining optical fiber laser diode module with high optical coupling efficiency has been realized.

Furthermore, according to the present invention, there is provided a polarization-maintaining optical fiber diode module which has the advantage of being able to separate the return light from the optical fiber into each polarization component and detect them separately in addition to the above-mentioned length D. can be realized.

These polarization-maintaining optical fiber laser diode monoles according to the present invention bring great effects when applied to 61-side technologies such as coherent communication and optical fiber wiring.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of a laser diode monolith with wavefront-preserving light according to the present invention. FIG. 5 is a schematic diagram of another embodiment of the present invention, and FIG. 6 is a polarization-maintaining optical fiber diode according to the present invention. A schematic illustration of a specific drawing example of 7 joules is shown in Fig. 1. Fig. 7 is a perspective view of the optical fiber core holder, and Fig. 8 is a plan view and both end views of the lens holder.・Raede diode, 2... polarization maintaining optical fiber, 3... ball lens, 4... Rochon prism,
5... Mechanical central axis of the module, 10...
-FUMIN-120... L-shaped metal fitting, 21... Core for optical fiber, 22... Core holder, 23... Lens holder.

Claims (1)

[Claims] 1. A polarization-maintaining optical fiber laser diode module that optically couples a polarization-maintaining optical fiber and a Rade diode, which comprises a Rade diode, a ball lens, a Rochon prism for polarization separation, and a polarization plane. storage optical fibers in this order and such that the central axes of the optical fibers and ball lenses coincide with the mechanical central axis of the module, and the optical axis of the radar diode deviates from the mechanical central axis, and The optical surfaces of the Raded diode, Rochon prism, and optical fiber are all configured to have an angle of inclination to a plane perpendicular to the mechanical center axis, and where tl is the distance between the center of the laser diode and the ball lens. tl: Distance between the center of the spherical lens and the optical fiber f: Focal length of the spherical lens ωLD' Gown beam spot size of the laser diode ωF Gown beam spot size of the binary fiber is configured to be satisfied simultaneously. Polarization preserving optical fiber led diode module. 2. In a polarization-maintaining optical fiber laser diode module that optically couples a polarization-maintaining optical fiber and a laser dimer, a Raded diode, a ball lens, a Rochon prism for polarization separation, and a polarization-maintaining optical fiber are combined. Jk order, and arranged so that the central axes of the optical fiber and the ball lens coincide with the mechanical center +1tlt line of the main unit, and the optical axis of the radar diode deviates from the mechanical central axis, and The optical surfaces of the Raded diode, Rochon grism, and optical fiber are all configured to have antenna angles with respect to a plane perpendicular to the mechanical center axis, and the distance t2 between the Raded diode and the center of the spherical lens is expressed by the following formula. Distance f between the center of the two-sphere lens and the optical fiber: Focal length of the spherical lens ωLD: I Gaussian beam spot size of the laser diode ωF = Gaussian beam spot size of the optical fiber. A polarization-maintaining optical fiber led diode monoyl whose distinctive feature is a configuration in which seven mirror buttons are placed between the led diode and the ball lens to reflect the light emitted from the optical fiber.