Available Photonics Experiments:

P5873 Glass fibre optics
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  • Coupling of light to fibres
  • Coupling Optics
  • Diode laser
  • Characterization of glass fibres
  • Cutting of fibres
  • Signal transfer via glass fibres
  • Speed of light
  • Examples of investigations and measurements
OX General set-up
This set-up has been made with a multimode fibre. Because of didactic reasons a bare fibre without extra protective coating has been selected. The cut and cleaved fibre is put into the groove of holder D and carefully fixed with the two magnets. The laser diode in its housing (A) is mounted on a four axes fine adjustment holder. A Peltier cooler and a thermistor for measuring the laser diode temperature are incorporated in the housing. The laser diode emits a maximum power of 50 mW as laser of class 3B.
A microscope objective (B) collimates the laser diode radiation.
The module C consists of a fine adjustment holder with four axes and an objective of smaller focal length to focus the collimated laser diode radiation in such a way that an effective coupling to the fibre is ensured. 1000 m multimode fibre (13) are coiled up on a drum.
The second fibre holder is mounted on a hinged joined angle connector.
The module G consists of the detector with a PIN photodiode and is mounted on top of the pivot arm of the module E. By turning the arm the angle resolved intensity distribution either of the laser diode or the fibre output can be measured. The module is connected to the signal conditioner box (P) where a BNC socket is provided to connect the output either to an oscilloscope or digital multimeter.
OX Properties of diode laser
By means of the set-up shown on the left the intensity distribution of the laser diode is measured. For this reason the laser diode module is set quite near to the rotation joint so that the unavoidable distance L from the axis of the rotation joint is a minimum. To measure the intensity distribution as a function of the angle with reference to another axis of the laser diode, the latter one can be rotated in its holder. With the same set-up, but the detector under 00 to the laser diode, the output power is measured as a function of the injection current and the temperature of the laser diode. Attention has to be paid to the fact that the detector does not approach saturation, which can be assured by choosing the distance to the laser diode in an appropriate manner.
OX Characterization of glass fibres
The pivot arm carrying the is used to measure the angle resolved intensity distribution. The smallest distance is predetermined by the rotation joint. The power is measured for different angles. Here, too, we use modulated light to eliminate the influence of environmental disturbances.
In determining the numerical aperture we will meet some physical effects which make the interpretation of the measured values a bit difficult. We are speaking about the cladding waves which leave the fibre together with the core waves simulating an aperture which is just too high. At larger distances of the detector this influence is remarkably reduced.
OX Speed of light
Another very interesting experiment is the measurement of the transit time of light through the fibre. The set-up is modified so that the detector is again next to the end of the fibre in holder E. The detector is connected to the signal conditioning box (module P) and the shunt is set to 50 W to reduce the rise time of the photodiode to the nano second range. The output of the signal conditioning box is connected to the first channel of the oscilloscope. The second channel is connected to the monitor exit of the modulation output at the control unit ED-0020 (module H). The difference in time of the rising edges of the start pulse and the photodetector signal corresponds to the speed of light and the length of the fibre
  • P5873 Glass fibre optics (XP-1900) consisting of:
12E-02401optical fiber cleaver and breaker S315
22E-02501Adjustable plastic cover stripper 103-S
32E-02901IR converter screen 0.8 - 1.6 �m
43L-03601BNC connection leads, set of 2
54B-01701Optical glass fibre, length 1000 m, core 50 �m multi mode
6ED-00201Digital diode laser controller
7ED-00601Photodetector signal conditioning box
8MC-02601Optical rail MG 65, 500 mm
9XM-00201Module A - Diode laser head, adjustment holder
10XM-00361Module B - Collimating optics on carrier
11XM-05101Coupling optics, microscope objective x 20 with XY- adjustment holder
12XM-05201Bare fibre holder with translation stage
13XM-05401Module E, bare fibre holder on rotation stage
14XM-11601Module G, SiPIN photodetector with mounting plate C25
 Required Options:  
 TP-01001Oscilloscope 100 MHz digital, two channel
 4B-01601 Optical glass fibre, length 1000 m, core 9 µm mono mode
 4G-01701 Multimode optical fibre 5000 m, 50/125 µm, on bobbin