JPS6341814A - Method and device for matching optical axes between semiconductor element and optical transmission line - Google Patents

Abstract

PURPOSE:To attain optical axis matching a having stable optical coupling efficiency by finding out the relation of the optical coupling rate to a relative position between a semiconductor element and an optical transmission line and using a position corresponding to its gravity as an optimum position to execute the optical matching. CONSTITUTION:An arithmetic unit 16 scans an optical axis adjusting device 17 at a fixed internal while oscillating the semiconductor laser element 1 by a fixed output and stores the outputs of a position detector and a photodetector 9 in its memory. In addition, the arithmetic unit 16 calculates a gravity position based upon a specific formula by using the output power of an optical fiber as a positional function on the basis of the stored data and drives the device 17 so that the optical fiber is positioned on the gravity position. The output power of the optical fiber 1 is scanned at a rough interval at first to detect a position on which a signal can be detected and then scanned in the (x)-(z) directions to match the optical axis with a position corresponding to the gravity position of optical coupling rate distribution. Thus, optical axis matching having highly stable optical coupling rate can be attained.

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention combines optical axis alignment of a semiconductor device such as a semiconductor laser device or an avalanche photodiode (hereinafter referred to as rAPD device) and an optical transmission line with a stable optical coupling rate. The present invention relates to a method and device for optical axis alignment.

<Technical Background of the Invention> In recent years, with the development of optical communication technology that uses optical fibers as optical transmission lines, it has become more and more efficient to transmit light emitted from semiconductor laser elements to optical transmission lines such as optical fibers and cell lenses. In order to satisfy this need, conventionally, as shown in FIG.
The optical transmission line 5 is moved in the x and X directions by operating the manipulator 6, and the optical position of the semiconductor laser element 1 and the input end 4 is changed to change the optical position of the semiconductor laser element 1 and the input end 4. I was doing alignment. A photodetector 9 for receiving output light 8 is provided on the output end 7 side of the optical transmission line 5 of this device, and the maximum light output of the photodetector 9 when the manipulator 6 is operated to observe its output. The optical axis was aligned so that the position of the optical transmission line 5 was determined at the point.

However, the above-mentioned optical axis alignment between the semiconductor element and the optical transmission line requires a very delicate operation, is inefficient, and has low precision. For this reason, the above-described apparatus has been operated in combination with a servo circuit as shown in the block diagram of FIG. That is, it includes a servo mechanism 11 that drives the manipulator 6 in the X direction and a servo mechanism 12 that drives the manipulator 6 in the The output is compared by the feedback circuit 14, and the difference between the two is alternately applied to the servo mechanisms 11 and 12 by switching the gate circuit 15, thereby controlling the manipulator 6.

Therefore, the holding value of maximum output holding #13 and the photodetector 9
When the outputs of servo 8! and 8! match, the output of the feedback circuit 14 becomes zero, and servo 8! Since the structures 11 and 12 are stopped, the optical axes can be aligned automatically.

<Problems to be Solved by the Invention> However, the conventional method for aligning the optical axis of the semiconductor element and the optical transmission line described above has
The emission intensity distribution in the Y direction (Il has multiple peak values as shown in FIG. 7. Therefore, for example, when the maximum output holder 13 holds the value of peak P, the servo circuit in FIG. 6 In the device combined with the peak P, it follows the peak P and stops at the peak P2 position, and the position is not adjusted to the higher intensity peak P1, so the optical axis alignment is performed at the peak P with low coupling efficiency.
It will be adjusted to match the two conditions.

This is 8! P2 has a smaller allowable amount than the original optical axis center, and optical coupling tends to become extremely unstable.

On the other hand, the peak position of the optical coupling ratio between the semiconductor element and the optical transmission line is not necessarily at the center of the optical axis. In other words, as shown in Figure 8, the relationship between the optical coupling rate and the amount of optical axis deviation between the semiconductor laser element and the multimode fiber processed with the tip lens is determined by the outside of the emission intensity distribution of the semiconductor laser element and the finish of the fiber lens. Due to variations or slight angular deviations, the optical coupling rate will have an asymmetric distribution. In this case, if the optical axis is aligned with the peak position of the light intensity as in the conventional method, the optical axis misalignment tolerance will be much stricter than in the original optical axis centering method, so the stability of the optical coupling ratio will be affected. becomes worse.

In particular, when the optical fiber used as the optical transmission line is a single mode type, the optical axis alignment position accuracy is required to the order of 0.1-, so it takes a long time to scan the entire range.

This invention relates to the above-mentioned semiconductor laser device, and more generally to the conventional semiconductor laser device and the optical transmission path in which the optical axis is aligned to the peak position of the emission intensity distribution in the optical axis alignment between the semiconductor device and the optical transmission path. This was developed in order to eliminate the drawbacks of optical axis alignment methods, and attempts to provide a method for optical axis alignment such that stable optical coupling efficiency between a semiconductor element and an optical transmission line can be obtained.

Another object of the present invention is to provide a device capable of aligning optical axes between a semiconductor element and an optical transmission line so as to have stable optical coupling efficiency.

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted various studies and found that when aligning the optical axis of the semiconductor element and the optical transmission line, the optical axis deviates from the center. In order to avoid following sub-peaks, the optical coupling rate distribution of the relative positions of the semiconductor element and the optical transmission line is determined, and the optical axis is set at the optimum position corresponding to the mathematical center of gravity of the optical coupling rate distribution. I realized that by combining these two elements, it would be possible to align the optical axes with a stable optical coupling rate, and was able to complete this invention.

That is, one aspect of the present invention is that when aligning the optical axes of the semiconductor element and the optical transmission line, the relationship between the optical coupling rate and the relative position of the semiconductor element and the optical transmission line is determined, and the position corresponding to the center of gravity is set as the optimum position and the optical axis is aligned. It is characterized by alignment.

In this invention, the position corresponding to the center of gravity of the optical coupling rate distribution with respect to the relative position of the semiconductor element and the optical transmission line is determined by calculating the coordinate R corresponding to the mathematical center of gravity as a function of the position coordinates. represents the optical coupling rate distribution, and if the optical coupling rate distribution is centered at the peak position and has a symmetrical and unimodal profile as shown in Figure 1, the center of gravity coincides with the peak position,
If there are multiple peaks (for example, two peaks), they are located on the center line of symmetry of the two peaks, as shown in FIG.

Another aspect of this invention is a scale adjustment device that freely changes the relative position of the semiconductor element and the optical transmission line, and detects the relative position of the semiconductor element and the optical transmission line, and generates an electrical signal proportional to the relative position. a position detector that measures the optical coupling ratio of the relative position 1 of the semiconductor element and the optical transmission line and converts it into an electrical signal; An arithmetic device that uses a signal to calculate a position corresponding to the center of gravity of the optical coupling rate distribution of the relative position of the semiconductor element and the optical transmission line as a value corresponding to the mathematical center of gravity as a function of position coordinates, and a calculation result of this arithmetic device. According to the above tone! The optical axis alignment of a semiconductor element and an optical transmission line is characterized in that it consists of a servo mechanism that drives one device.

As described above, since the optical axes of the semiconductor element and the optical transmission line of the present invention are aligned using the position corresponding to the center of gravity of the optical coupling ratio distribution as the optimum position, optical axis misalignment and optical coupling ratio Even if the distribution is simple and asymmetrical and does not have a single peak with good symmetry, the optical axis can be aligned at the optical axis center position with a highly stable optical coupling rate.

Embodiments Next, a method for aligning the optical axis of a semiconductor element and an optical transmission line according to the present invention will be described based on an apparatus used for carrying out the method.

Embodiment Example 1 FIG. 3 is a perspective view of essential parts showing a schematic configuration of an optical axis alignment device for a semiconductor device and an optical transmission line according to the present invention, in which 1 is a semiconductor laser device, 5 is a semiconductor laser device 1, and 5 is a semiconductor laser device 1. 9 is a photodetector for measuring the optical output power of the optical fiber; 17 is a device for detecting the position of the optical fiber 5 and aligning the optical axis by driving a pulse motor; This is an arithmetic device that reads device detection data consisting of a detector 9 and a position detector and controls the yJR adjustment operation of the optical axis adjustment device fi17.The arithmetic device 16 uses a microcomputer to control the semiconductor laser element 1 with a constant output While oscillating with Calculate the center of gravity position according to the above-mentioned calculation formula (1) using the output power as a function of position, and operate the optical axis adjustment device 17 so that the optical fiber is located at the calculated center of gravity position.All of the above operations are performed by calculations. It is controlled according to an internal program preinstalled in the device 16.

With this configuration, in order to shorten the measurement time, the output power of the optical fiber 1 is scanned at coarse intervals at first to find a position where a signal can be detected. Next, fine scanning is performed in the XpYp'' axis direction (7, axis is the optical axis direction),
The optical axis may be aligned to a position corresponding to the center of gravity of the optical coupling rate distribution.

This method of aligning the optical axis using two-step scanning is particularly effective when the optical fiber 2 is a single mode fiber with a small tolerance.

Embodiment 2 FIG. 4 is a perspective view of a main part showing a schematic configuration of the second *male side of the semiconductor element and the optical axis alignment device for the optical transmission line of the present invention, and 1a is an avalanche photodiode ( APD
5 is an optical fiber, 18 is a stable light source that injects a constant optical power into the optical fiber, 17 is a fiber position detection and TA adjustment mechanism, and 16 is an arithmetic unit.

The operating mechanism of the semiconductor device and the optical axis alignment device for the optical transmission line shown in FIG. It can be used almost as is for one person.

Therefore, if you use the device of this embodiment, you can simply change the parameters of the internal program without changing the configuration of the device, regardless of whether it is a light emitting element or a light receiving element, or whether the optical fiber is multimode or single mode. So, I can handle it.

<Effects of the Invention> As is clear from the above explanation, according to the optical axis alignment method of the semiconductor element and optical transmission line of the present invention, when the relationship between the optical axis misalignment and the optical coupling rate does not become a simple single peak peak, However, since the optical axis can be aligned to a stable optical coupling ratio position, adjustment time can be shortened and yields can be improved.

[Brief explanation of drawings]

Figures 1 and 2 are profile diagrams in which the optical coupling rate distribution of the semiconductor element and the optical transmission line is symmetrical, with single and bimodal profiles, respectively, and Figure 3 is the optical axis alignment device for the semiconductor element and the optical transmission line of the present invention. A perspective view of main parts showing the schematic configuration of the first embodiment, the fourth
The figure is a perspective view of a main part showing a schematic configuration of a second embodiment of the optical axis alignment device for a semiconductor element and an optical transmission line according to the present invention, and FIG. FIG. 6 is a block diagram of the servo circuit combined with the optical axis alignment shown in FIG. 5; FIG. 7 is an explanatory diagram showing the state of the peak value of the emission intensity distribution of the semiconductor laser element; FIG. 8 is state B when the optical axis deviation amount and optical coupling efficiency have an asymmetric distribution
FIG. In the drawings, 1: semiconductor laser element, 1a: APD element, 5: optical transmission line, 9: photodetector, 16: arithmetic unit. Figure 1 Figure 2 Figure 4 Figure 5 87''1 Figure 6 Figure 7■ Figure 8 Optical axis deviation 5μm/scale

Claims (2)

[Claims] (1) When aligning the optical axes of the semiconductor element and the optical transmission line, find the relationship of the optical coupling rate with respect to the relative position of the semiconductor element and the optical transmission line, and also calculate the optical coupling rate distribution with respect to the relative position of the semiconductor element and the optical transmission line. A method for aligning optical axes between a semiconductor element and an optical transmission line, characterized in that the optical axes are aligned using a position corresponding to the center of gravity as the optimum position. (2) an adjustment device that can freely change the relative position between the semiconductor element and the optical transmission line; a position detector that detects the relative position of the semiconductor element and the optical transmission line and generates an electrical signal proportional to the relative position; an optical coupling rate measuring device that measures the optical coupling rate of the relative position of the semiconductor element and the optical transmission line and converts it into an electrical signal; and an optical coupling rate measuring device that measures the optical coupling rate of the relative position of the semiconductor element and the optical transmission line, and transmits the optical signal to the semiconductor element using the electrical signal sent from the position detecting device and the optical coupling rate measuring device. an arithmetic device that calculates a position corresponding to the center of gravity of the optical coupling rate distribution of the relative position of the road as a value corresponding to the mathematical center of gravity as a relationship of positional coordinates; and a calculation device that drives the adjustment device in accordance with the arithmetic result of the arithmetic device. 1. An optical axis alignment device for a semiconductor element and an optical transmission line, characterized by comprising a servo mechanism for aligning a semiconductor element and an optical transmission line.