JPS5827113A - Optical transmission device - Google Patents

Abstract

PURPOSE:To permit transmission of light to desired places by delicate adjustment of the optical transmission paths of two near parabolic rod lenses which are so disposed as to face each other at the end faces by providing a flat plate which permits the transmission of light obliquely on one end face of said two rod lenses. CONSTITUTION:Lenses 5, 6 which are provided to face to each other are constituted into a columnar shape in such a way as to have gradually smaller refractive indices the nearer the outer side from the center. A flat plate 7 permitting the transmission of light is disposed at one of their opposing end faces, for example, the end face of the lens 5 at an angle alpha. An adhesive agent 8 permitting the transmission of light is filled therebetween to adhere the lens 5 and the plate 7. If the plate 7 is not adhered, the light made incident from the point A focuses at the point B on the end face of the lens 6, but when the plate 7 is adhered, the agent 8 acts as a prism and the incident light from the point A focuses at the point C. Therefore, the focusing position of light is controlled by controlling the angle of inclination of the plate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to provide an optical transmission device that can transmit light to a predetermined location by finely adjusting the transmission optical path of two converging rod lenses.

With the recent development of optical communications, there are expectations for the practical implementation of large-capacity transmission. For this purpose, transmission using a single mode fiber is being considered, but the light propagating portion C
Even if the core is for long wavelengths, it has a small diameter of more than 10 μm, making it extremely difficult to couple a laser with a fiber or create optical devices such as a demultiplexer. For example, the oscillation wavelength is 1.3
FIG. 1 shows the coupling characteristics when a semiconductor laser oscillating in a single mode of μm is fully coupled to a tapered spherical optical fiber with a core diameter of 10.8 μm. FIG. 1 shows all the percentages of decrease in output from the original fiber when the fiber is shifted from the optimum coupling position in a direction perpendicular to the fiber axis. The X direction is parallel to the LD active layer and the y direction is perpendicular. As can be seen from this figure, when coupling the laser and the original fiber so that the output drop from the optimal coupled output is within 1 dB, the alignment of 8 degrees must be 0.25 μm or less. It is very difficult to control such positioning with a normal fine movement device. Furthermore, if solder is used to fix the semiconductor laser and the optical fiber, the optimum bonding position will shift due to thermal expansion. For these reasons, various means have been proposed for coupling a semiconductor laser and a single mode fiber, but no means for practical use has yet been developed. For example, in the example shown in FIG. 2, the accuracy of alignment with the optical fiber 4 is completely relaxed by bonding the microsphere lens 2 to the end face of the semiconductor laser with adhesive 3, but the resonant surface of the laser 1 Since the lens 2 is bonded on top, there are drawbacks such as increased threshold current and thermal distortion on the resonant surface, which impairs reliability.

The present invention is intended to provide an optical transmission device that requires extremely high alignment accuracy by simple means, and embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows a basic embodiment of the invention. 5
．． 6 are convergent rod lenses. This lens ε, 6 is columnar and has a refractive index that gradually decreases from the center to the outside, and has a period length of -. The end surfaces of the lenses 5 and 6 are arranged so as to face each other, and a flat plate 7 that transmits light and sound is placed on the end surface of one lens 6 at an angle α, and an adhesive 8f that transmits light is placed between the end surfaces of the lens 6. 5 and the flat plate 7.

When lenses 5 and 6 are arranged with their axes aligned, the light incident from point 11 A on the end face of lens 5 becomes a parallel beam after passing through lens 5, so a collimating system can be constructed with two lenses at 5°. . When the flat plate 7 is not bonded, the light incident from point A is focused on point B on the end surface of the lens 6. However, when the flat plate 7 is glued, the adhesive 8 acts as a prism, and the light E entering from the point A is focused on the zero point. Therefore, by controlling the angle of inclination when bonding the flat plate 7, the focusing position of the light can be controlled. The refractive index of the adhesive (i=n, the inclination angle of the flat plate 7 is α.

If the angle of axis deviation of the parallel beam is all θ, then = (n-1) α
There is a relationship between Also, if the total distance from the axis to the focusing position is d, then d=θ-L/2yrN, :(n-1) a ・L
There is a relationship of /2πN. Here, L is the focusing lens 6
．． 6, N is the refractive index of the lens 6.6. As lenses 5 and 6 (φ2.L=20.a, N=1
．． FIG. 4 shows the relationship between α and d when the converging lens 6) and the resin with l1=1.5 are used. It can be seen that if the angle '(i70.01 degrees) is controlled from this angle 7, the position can be controlled by 0.18 μm.As a device for controlling the angle, for example, a micrometer head 9a as shown in FIG.
, 9b, and 9c, and the head interval Li is 10 cm, if the head is moved by 1 μm of the minimum scale, the angle will move by 0.00057°, and therefore the focusing position will move by about 0.01 μm. Accuracy 0 to within 1dB
．． It can be seen that there is very good controllability for 26 μmK.

Furthermore, if ultraviolet curing resin is used for bonding the flat plate 7 and the lens 5, the manufacturing device will not expand due to temperature, so that the bonding can be performed with high precision.

Therefore, if light is introduced from point 0, it can be emitted to point A. It would be good if the laser beam could enter point iB correctly, but it often happens that the laser beam enters deviated, and even if it enters deviated from the 0 point, the trajectory is corrected by the flat plate 7 and adhesive 8, and the light can be emitted to point A.

An example of this implementation is shown in FIG. 6. 11 is a single mode fiber attached to the end face of the lens 5. Even if the light emitted from the laser 10 does not hit the center of the lens 6 correctly, it can be correctly directed into the fiber 11 due to the prism effect of the adhesive 8.

FIG. 7 shows another embodiment according to the present invention. Focusing Oy7
Drain lenses 12a, 12b, 12c are optical connectors 13a,
13b and 13c, forming a collimating system. And in the middle is half mirror 1
3 is inserted, and the light incident from the original fiber 14a) - the light transmitted through the mirror 13 is transferred to the fiber 14b.
Vc, and the reflected light enters the fiber 140 [. At this time, flat plates 15b and 1esc and adhesives 16a and 16b are used for fine adjustment of the focusing position. flat plate 16b
, 1rsc, it becomes an optical demultiplexer.

Note that the flat plate may be attached to either of the two lenses using adhesive.

Two cylindrical focusing rod lenses are arranged with their end surfaces facing each other, and a flat plate through which light passes is tilted to at least one of the opposing end surfaces of the two focusing rod lenses. The main feature is that the focusing rod lens and the flat plate are bonded by filling the space between the flat plate and the end face with a transparent adhesive, and by fully adjusting the angle at which the flat plate is bonded, Light that has passed through one lens can be accurately transmitted to a predetermined location on the end face of the other lens.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing all the coupling characteristics of a semiconductor laser and an optical fiber in a conventional example, Fig. 2 is a principle diagram showing all the coupling states of a semiconductor laser and an original fiber in a conventional example, and Fig. 3 is a characteristic diagram showing all the coupling characteristics of a semiconductor laser and an optical fiber in a conventional example. 4 is a characteristic diagram for explaining the device, FIG. 5 is a perspective view of the device for manufacturing the entire device, and FIG. 6 is a diagram of the optical transmission device in an embodiment of the present invention. Strabismus E5, 8, 12 a, 12 b, 1
2 c ・----Focusing aperture, torrent lens, 7, 16
b, I E5 c...-flat plate, 8゜1eb, 16
c...Adhesive. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 35iI @ 4 Figure 5 - L-1

Claims (1)

[Claims] Two columnar focusing rod lenses installed so that the refractive index gradually decreases from the center to the outside are arranged so that their end surfaces completely face each other, and the relative orientation of the two focusing rod lenses is At least one of the end faces of the lens is provided with a flat plate that allows light to pass therethrough, and an adhesive that allows light to pass through is filled between the flat plate and the end face, and the focusing rod lens and the flat plate are fully bonded. Features of optical transmission equipment.