JPS61223528A - Measurement for propagation loss of lightwave guide - Google Patents

Abstract

PURPOSE:To achieve a very high working efficiency and measuring accuracy, by measuring emission light from an output prism for measurement only at two points. CONSTITUTION:An output prism 12 for monitoring is fixed at the position separated by Z3 from the incidence point Li of a propagation light and the emission light power from the prism 12 is represented by P deg.3 when a prism 7 located at the position (Z3>Z1) separated by Z1 from the incident position of the propagation light is not pressed on a lightwave guide 2. When the prism 7 is pressed on the surface of the lightwave guide 2, light comes to be emitted from the prism 7 by combination of the prism 7 and the lightwave guide 2. As the pressing is intensified, the emission light power P1 from the prism 7 grow gradually but on the contrary, the emission light power P3 from the prism 12 weakens gradually. At this point, as the decrement DELTAP'3identicalP deg.3-P'3 of the emission power from the prism 12 is proportional to the emission power P1 from the prism 7, the propagation loss coefficient of the lightwave guide 2 can be determined.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the propagation loss of an optical waveguide using a prism.

[Summary of the invention]

This invention simplifies measurement by measuring the light emitted from the measurement output prism at only two locations on the optical waveguide and determining the propagation loss of the leading waveguide, while also allowing highly accurate measurement. That is.

[Prior art] In recent years, research on various devices using optical waveguides has been actively conducted, and as a result, due to the nature of the guiding waveguide,
Many methods have been proposed for measuring propagation loss, which is an important factor.

Figures 4 and 5 @'/: For example, Tokuko Sho 59-48
335 is a diagram illustrating a conventional method for measuring propagation loss of a leading wavepath disclosed in Publication No. 335. FIG. In FIG. 4, 12 is a monitor output prism, 13 is a monitor output prism fixing jig, 14 is monitor output light taken out to the outside by the monitor output prism 12, and 15 is monitor output light 1.
This is a photodetector that detects the power of 4. Here, the monitor output prism 12 is fixed at a position farther away from the output prism 7 in the propagation direction so that the output prism 7 can move within the required measurement range.

Next, the operation will be explained.

FIG. 5 shows how the power P of light propagating through the thin film guide waveguide 2 attenuates as the propagation path separates.

The power P of the light propagating in the 1111 optical waveguide 2 is expressed as p - poe as described above. Q2
A monitor output prism 12 is fixed at the point. When the output prism 7 is removed from the measurement point Q1, the power P attenuates along the ζ solid line, and the power P2 of the thin film guiding waveguide 2 at point Q2 becomes P2=Poe-, The power of the monitor output light 14 from the monitor output prism 12 is P3.
becomes. At this time, the decoupling efficiency η2 of the output prism 12 for monitoring is as follows: When the output prism 7 is installed at the measurement point Q1, the power P1 of the output light 9 is extracted at one point, and the power P is attenuated along the broken line. Then, N at Q2 point
The power P'2 in the film optical waveguide 2 is expressed as P'2 = (1-
"f)1)Pie-", and the power of the monitor output light 14 from the monitor output prism 12 becomes P3. This is what happens. Since the monitor output prism 12 is fixed, its decoupling efficiency is constant regardless of the removal of the output prism 7 and mI, so η°2−η
'2, that is, the monitor output power of the monitor output prism 12 when installed, so it is measured.

Therefore, the decoupling efficiency η1 of the output prism 7 is determined. Furthermore, since this decoupling efficiency can be found in the same way when the measuring point J21 is changed, the output power P1 of the output prism 7 is corrected by the decoupling efficiency η1, and the logarithm of distance versus output power (a = bow npo + convergence) is calculated. By first finding a straight line PsP+, it is possible to find the propagation loss from its slope.

(Problems to be Solved by the Invention) As described above, in the conventional measurement method, each time the position of the output prism 70 is changed, the distance traveled by the prism 7 and the distance of the output light from the output prism 7 and the monitor output prism 12 are measured. Although the power is measured and the propagation loss is determined based on these measured values, it is necessary to change the position of the output prism 7 many times in order to improve the measurement accuracy. However, since installation of the prism requires delicate adjustments, the number of times the distance traveled by the prism 7 is measured increases, resulting in larger measurement errors and, as a result, a decrease in the measurement accuracy of propagation loss. There was a point. Another problem is that the measurement time increases as the number of measurements increases.Moreover, as the measurement time increases, the prism and optical waveguide become more contaminated during the measurement, which significantly reduces the coupling efficiency between the prism and the optical waveguide. As a result, the prism and optical waveguide must be cleaned many times before, during, or after the measurement, resulting in a problem that the measurement time becomes even longer. Furthermore, since the prism fixing jig must be removed every time the position of the prism 7 is moved, there is a problem in that the measurement work is extremely complicated.

[Means for solving problems]

This invention was made in order to solve the above-mentioned problem, and a measuring output prism is disposed between the incident position of light into the leading waveguide and the monitor output prism, and The light emitted from the measurement output prism is measured only at two arbitrary locations between the phase ratio cabulisms.

[Effect]

In this invention, since the light emitted from the measurement output prism is measured at only two locations, work efficiency is significantly improved and measurement accuracy is extremely high.

〔Example〕

Below, an embodiment of the present invention will be described in FIGS. 1 and 2.
This will be explained according to the diagram. FIG. 1 is a block diagram of a method for measuring the propagation loss of a leading waveguide according to the present invention. In FIG. 1, light emitted from a light source 16 is attenuated by an attenuator 17,
After being chopped by the optical chopper 18, it enters the prism 4. The attenuator 17 is used for guiding waveguides that would cause optical damage to strong incident light (e.g.
When measuring the propagation loss of an optical waveguide (an optical waveguide in which Ti is diffused in a LiNbO5 substrate), the attenuator 17 may not be used in the case of a leading waveguide that does not cause optical damage. Further, the reason why the optical chopper 18 is used is to block noise light other than the incident light and to obtain a synchronization frequency when detecting the output signal with the lock-in amplifier 24.

This optical chopper 18 is driven by a chopper driver 23. The light incident on the prism 4 is introduced into the optical waveguide 2 and propagates through the optical waveguide 2. A monitor output prism 12 is fixed at a position 73 away from the incident position of the propagated light, and is located 73 degrees away from the incident position of the propagated light! Let Po3 be the power of the light emitted from the prism 12 when the prism 7 (Z3>21) is not pressed onto the optical waveguide 2. When the prism 7 is pressed onto the surface of the optical waveguide 2 using a fixing jig (not shown), light is emitted from the prism 7 due to the coupling between the prism 7 and the optical waveguide 2. As the pressure is strengthened, the power P1 of the light emitted from the prism 7 gradually increases, and the power P3 of the light emitted from the prism 12 gradually weakens. At this time, the decrease in the power of the light emitted from the prism 12, P'33P'3-P'3, is proportional to the power P1 of the light emitted from the prism 7, so ΔP3-TlPl...
... is expressed as (1). If this relationship is represented on a graph, it will look like a straight line 40 in Figure 2, and the slope of this straight line is T.
It is 1. Next, the prism 7 is moved 7 degrees from the incident position of the propagating light.
Move to a position 2 apart (Zt < 22 < 23),
If the power of the light emitted from the prism 12 when the pressure is strengthened is P23, and the power of the light emitted from the prism 7 at this time is P2, then ΔP"33P"3-P'3 = T2 as in equation (1). P2...
...It is expressed as (2). If this relationship is represented in a graph, it will look like a straight line 50 in FIG. 2, and the slope of this straight line is T2.

On the other hand, the decrease ΔP3 in the optical power emitted from the prism 12 when the prism 7 is crimped is the amount that the optical power P1 originally emitted from the prism 7 propagates through the optical waveguide 2 from 21 to 23, and the power emitted from the prism 12. Therefore, if the coupling efficiency of the prism 12 is δ and the propagation loss coefficient of the optical waveguide 2 is α, then ΔP3−δP, e−cc(7J−g+)
(The relationship between 31 and 92- is established. Similarly, when the measurement output prism 7 moves to 72, ΔP"3-δP2e-"'"7°-" -...-(4
). By substituting (1) and (2 into (3) and (4) and removing δ, Z3, Pl, and P2, we can obtain by plotting the values, and Zl and Zλl are the distances of the measurement output prism 7. Since it is obtained by measurement, the propagation loss coefficient α of the optical waveguide 2 is determined by equation (5).In actual measurement, the light emitted from the prism is condensed by the condensing lens 19, 21 and sent to the photodetector 11. After being converted into a voltage, it is input to a detector such as a lock-in amplifier 24 and read as a voltage.

As explained above, in the method for measuring the propagation loss of the optical waveguide 2 according to the present invention, the fixed position of the output prism 7 for measurement is 2.
Since there are only two locations, there is no deterioration in measurement accuracy of propagation loss due to measurement error in the position of the measurement output prism 7, which is a problem with the conventional method, and very accurate measurement can be performed. In addition, the method for measuring the propagation loss of the optical waveguide 2 according to the present invention can reduce the time required to remove and attach the prism fixing jig many times and to clean the prism and the leading waveguide, as in the conventional method. This is a method with significantly improved work efficiency.

Next, another embodiment of the present invention will be described with reference to FIG.

FIG. 3 shows another embodiment of the method for measuring propagation loss of an optical waveguide according to the present invention. In FIG. 1, the prism 4 is used as the method of light incidence, but any method may be used. For example, as shown in FIG. You may let them.

(Effects of the Invention) As described above, in the present invention, a measuring prism is disposed between the light incident position into the optical waveguide and the monitor phase ratio fog, and the measurement prism is disposed between the light incidence position and the monitor phase ratio fog. In addition to measuring the light emitted from the measurement output prism at only one location, the light emitted from the monitoring soil cabrism was also measured, and the propagation loss of the optical waveguide was measured based on these measured values. The number of measurements of the light emitted from the measurement output prism is significantly reduced, and the measurement accuracy is extremely high.In addition, the multiple removal and installation of the fixing jig for the measurement output prism requires work and cleaning of the optical waveguide. It is possible to provide a method for measuring propagation loss of a leading wavepath that can reduce the time required and significantly improve work efficiency.

[Brief Description of the Drawings] Fig. 1 is an explanatory diagram of a method for measuring propagation loss of an optical waveguide according to an embodiment of the present invention, Fig. 2 is an explanatory diagram for determining propagation loss, and Fig. 3 is an explanatory diagram of a method for measuring propagation loss of an optical waveguide according to an embodiment of the present invention. FIG. 4 is an explanatory diagram of a conventional method for measuring propagation loss of an optical waveguide, and FIG. 5 is a diagram showing propagation distance versus output power characteristics. 1... Waveguide light, 2... Optical waveguide, 7.
... Output prism for measurement, 12 ... Soil cabrism for monitoring, 16 ...
··light source. Patent Applicant: Tateishi Electric Co., Ltd. Figure 1 - How to Measure the Invention Part 11:
Light 3A 2nd figure [8-arrow tgisaruta Vθ theory sentry 3rd figure Sn1hi January/) One in 4 (power begging lt hosu figure f2;
Output for 7'-9) 1λm Figure 4 Sudden rise β Nine liquids ψ I & Adjustment trap member Loss Shi Rule λ Method showing the method Figure 5

Claims (2)

[Claims] (1) A measurement output prism that is attached to an optical waveguide and extracts the guided light propagating through the optical waveguide, and a measurement output prism that is located at a position where the guided light is incident on the optical waveguide from a position of the measurement output prism. In a method for measuring the propagation loss of an optical waveguide using a monitoring output prism fixed at a position away from the optical waveguide in the propagation direction, the output light from the monitoring output prism is measured, and the optical waveguide on the optical waveguide is Propagation of an optical waveguide characterized in that the propagation loss of the optical waveguide is determined by measuring the light emitted from the measurement output prism at two arbitrary points between the incident position of the wave light and the monitoring output prism. Loss measurement method. (2) Propagation of the optical waveguide by changing the pressure bonding force between the measurement output prism and the optical waveguide, and measuring the emitted light from the measurement output prism and the monitoring output prism each time the pressure bonding force is changed. A method for measuring propagation loss of an optical waveguide according to claim 1, characterized in that the loss is determined.