JPS5858008B2 - Laser power detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bolometer type laser power meter that propagates a laser beam whose power is to be measured through an optical waveguide and can measure the power with high sensitivity, and particularly relates to a detection device in the measurement system. It is related to.

Conventionally, a calorimeter used to measure laser power consists of the basic elements of a light absorber, a temperature detection element, and a calibration heater.

However, with this method, laser beams with a small emission area, etc.
When measuring the power of a laser beam with a large divergence angle that is emitted into space from an optical fiber or optical integrated circuit, it is necessary to increase the area of the absorber in order to absorb all the power. There are disadvantages such as sensitivity unevenness is likely to occur, the temperature increase is small due to the large heat capacity, making it difficult to increase sensitivity, and the time response is slow.

The present invention has been made in view of this point, and includes a temperature-sensitive resistor that also serves as an absorber for the laser light to be attached to an optical waveguide made of a material that is as transparent as possible, at least for the laser light to be measured. The main purpose of this invention is to provide a detection device that can be used to measure laser power with high sensitivity and precision, such as by making it into a small, high-sensitivity bolometer-type laser power meter.

Below, several embodiments of the laser power detection device of the present invention will be described in detail with reference to the drawings.

The optical waveguide 1 shown in FIGS. 1A and 1B is one of the basic embodiments of the present invention, and the optical waveguide 1 is made of a material that has low optical loss and is transparent at least to the light to be measured. In this case, it is tubular, and its end surface 1a is optically polished.

The outer wall of the optical waveguide 1 is surrounded by at least a portion in the circumferential direction, preferably the entire circumference as shown in the figure, and has a suitable length in the axial direction.
The temperature sensitive resistor 2 is provided closely.

Electrodes 3, 3 are attached to both ends of the temperature-sensitive resistor 2, so that a current can be passed through the resistor 2 via lead wires 4, 4, as shown by the arrow (■) in the figure.

In this way, a detection device 10 as a whole that absorbs laser light and detects its power is constructed, and this detection device 10 is called an optical waveguide bolometer (LGB) unit.

The laser beam E to be measured is supplied to the optical waveguide end face 1a of the unit or the detection device 10 from the small cross-sectional area output end face of the optical fiber F, etc., and as it propagates through the optical waveguide 1, it hits the temperature sensitive resistor 2. It gets absorbed.

The power of the laser beam E is measured, for example, by a measurement system as shown in the second figure.

This measurement system is of a highly general bridge type, in which the detection device or LBG unit 10 shown in the first diagram is inserted on one side, and resistors 5 having a known resistance value R on the other three sides.
...are arranged.

Of course, it is usual for this type of circuit to be provided with a galvanometer G1 power source V for balancing.

Means for detecting the circuit current, ultimately the current in the unit 10 (
An ammeter (such as an ammeter) A and a means for adjusting the current (in this case, a variable resistor r) are connected in series to the power supply (2).Measurements using such a measurement system are carried out as follows.

First, a suitable current 11 is applied to the temperature-sensitive resistor 2 from the power source 2 through the lead wire 4 and the electrode 3, and a certain resistance value, in this case the resistance value R balanced in the bridge circuit described above (of each resistor 5), is applied. (obviously the same as the value).

When the laser beam E to be measured is introduced into the optical waveguide 1,
The temperature-sensitive resistor 2 absorbs the power of the light, causing a temperature rise, and its resistance value changes, generally decreasing.

Here, while monitoring the galvanometer G, the current is adjusted and generally decreased by the current adjusting means r), so that the bridge circuit is balanced again and the resistance value of the temperature sensitive resistor 2 becomes the resistance value before the laser beam enters. Aim for the value R.

By reading the current value ■2 at that time with ammeter A,
The power of the laser beam E can be determined by the following formula in correlation with the current value (1) required to obtain the resistance value R of the temperature-sensitive resistor 2 before the laser beam is incident.

FIGS. 3A and 3B show other embodiments of the present device, which include a passing type and a terminal type.

The difference from the one shown in FIG. 1 is that the peripheral wall surface of the optical waveguide 1 is used as a scattering surface 1b (at least the portion facing the temperature-sensitive resistor means), and the absorption rate is improved by equivalently increasing the area.

The pass-through type shown in FIG. 3A has the advantage that output light similar to paraxial light (light that passes approximately along the optical axis without touching the wall surface) can be obtained, and that signal waveforms and the like can be monitored at the same time.

Since the terminal type shown in Figure 3B does not consider the passage and output of light, by creating a scattering section 6 at the center of the optical waveguide, light near the paraxial axis is scattered and absorbed by the wall surface.

Therefore, almost all of the optical power can be absorbed by the bolometer unit.

The number and shape of the scattering parts are arbitrary depending on the above purpose.

Glasses with low light absorption loss are suitable as transparent materials for optical waveguides, and among them, quartz glass is most suitable.

As the temperature-sensitive resistor, a semiconductor thermistor, a metal film, etc. can be used.

Although the diameter, length, and shape of the optical waveguide can be selected arbitrarily, they are designed depending on the characteristics of the object to be measured, such as wavelength and power level spread angle.

The scattering wall surface 1b may be an integral one that is directly worked on the peripheral wall surface of the optical waveguide 1, or may be made separately and assembled.

FIG. 4 shows an example of a mount structure 9 suitable for mechanically supporting each of the bolometer units 10 described above, in which the casing 9a is preferably filled with a heat insulating material 7, and the ends of the lead wires 4 are It is preferable to connect to the connector 8 so that connection with external measurement equipment is simple and reliable.

It goes without saying that the mounting structure itself is an arbitrary matter and is not limited to what is shown in the drawings.

As described in detail above, the present invention provides an optical waveguide means made of a material that is at least transparent to the light to be measured, preferably made of a transparent material such as quartz glass, and a temperature-sensitive resistor that serves as an absorber and a temperature detection element. We provide a laser power detection device or an optical waveguide type bolometer unit that converts laser power into an electrical quantity and detects it, and is an effective device that can be used in an optical power measurement system to perform highly sensitive and simple measurements. It is highly versatile for use in optical communication power measuring instruments, etc.

[Brief explanation of the drawing]

FIG. 1A is a perspective view of a basic embodiment of the laser power detection device of the present invention, FIG. 1B is a vertical sectional view thereof, and FIG. 2 is a schematic configuration diagram of an example of a measurement system including the detection device. 3
Figure A is a vertical sectional view of the second embodiment of the present invention, Figure 3B is a vertical sectional view of the third embodiment, and Figure 4 is a schematic diagram of a mount structure suitable for mechanically supporting the device of the present invention. Configuration cross section,
It is. In the figure, 1 is an optical waveguide means, 2 is a temperature-sensitive resistor, 6 is a scattering means, and 10 is the entire laser power detection device.

Claims (1)

[Claims] 1. An optical waveguide means made of a material that is at least transparent to the laser beam to be measured, and a temperature sensitive resistor means as a laser power absorber is attached to the optical waveguide means, A laser power detection device characterized in that the laser power can be detected by converting the laser power into an electric quantity. 2. The laser power detection device according to claim 1, wherein the temperature-sensitive resistor means is disposed over the entire circumferential area along the outer surface of the optical waveguide means. 3. The laser power detection device according to claim 1, wherein a wall surface of the optical waveguide means facing the temperature-sensitive resistor means is provided with a scattering surface for scattering light. 4. The laser power detection device according to claim 1, wherein a scattering means is arranged inside the optical waveguide means.