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Original Publication Date: 2000-Mar-01
Included in the Prior Art Database: 2003-Jun-11
Document File: 4 page(s) / 63K

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It is well known that the Infrared (IR) transceiver performance test is a very important stage of the research, design, development, manufacture and applications.

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  It is well known that the Infrared (IR) transceiver performance test is a very important stage of the research, design, development, manufacture and applications.

The conventional open space and pre-calibration test system has some very serious problems:
1) Environment background reflection in an open space site affects the test results, especially for the tests with low optical power levels.
2) The output optical power from a pre-calibrated light source is not stable due to its thermal performance.
3) In an open space test system, the optical power at the receiver side can not be very high to meet IrDa standard because it increases the optical power by decreasing the distance between the receiver and light source, but when the distance close to the dimensions of the light source, the distance-power square rule is not valid.

This paper provides a closure test system which is a combination of 50 um optical fiber system and a free space system. It gives the solutions for all the problems mentioned above.

The closure test system is divided into two subsystems: receiving test system and transmitting test system. This paper focuses on the receiving test system because the transmitting test system follows the same principle.

The receiving test system structure is shown in Fig. 1

The main laser <a> is the main light source with the wavelength of 870nm and very high optical output power of 170 to 200 mW to meet IrDa requirements.

The main laser diode drive <b> provides the pulsed current to the main laser. The TE cooler controller <c> provides the current to the built-in TE of the main laser and keeps the output optical power and the wavelength stable.

The optical power splitter <d> splits a small portion optical power, such as 1% of the main laser output optical power to the optical power monitor <e>. Since the optical power splitter has very stable the splitting ratio, the monitor can provide the compensation information or alarm in case when the main laser


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ages or some malfunction occurs in the main laser system.

The variable optical attenuator <f> can change the optical power to meet the whole dynamic range of the optical power up to 5 to 6 orders.

The sunlight simulation light source is a DC source which simulate the sunlight optical power intensity of 500 uW/cm2. The light source is not necessary a laser, a LED may be qualified for the application as long as the LED can couple enough optical power to the optical fiber. The optical power splitter <h> and sunlight simulation light source driver <i> form a close loop regulation to keep the DC optical power constant.

The following formulae are for the main laser selection

    P = PD * A / K where P is the laser optical power required PD is the maximum optical power intensity required at the photo detector of the IR transceiver under test. According to IrDa standard PD = 500 mW/cm2

    A is the maximum possible active area...