Therefore we can conclude that the propagation velocity of light in fiber is less than the propagation velocity of light in the air. This experiment by measuring the propagation time of a bunch of optical pulse signal in a certain length of fiber to calculate the speed of light propagation in optical fibers in order to calculate the average refractive index of the fiber. Enter a series of stable optical pulse signal input fiber and the fiber output end to accept these signals, due to the length of the fiber caused by a pulse signal time delay. Which the speed of light in fiber, L is the fiber length. Where is the speed of light in fiber, the speed of light in the air, the refractive index of air. The numerical aperture of the fiber. It should be obeyed by the manufacturer to ensure the quality of green laser pointer .
The numerical aperture of the optical structural parameters of the fiber, it means the ability of fiber to collect light, shown in Figure 2, it is defined as the sine of the angle of incidence of the beam just to satisfy the total reflection conditions and n0 the product, that is. Greater than the incident light from the cladding to leak less than the incident light may be bound to long-distance transmission in optical fibers. Can prove that is mainly determined by the core refractive index and the cladding refractive index. This experiment was calculated by measuring the divergence angle of the output spot. Light propagation in the fiber. In practical optical communication, part of the transmission of sound signals, such as language, music, and so on. This experiment will observe the process of the sound signal through the optical fiber transmission. The firm and strong package of green laser pointer can meet requirements.
Observed from the oscilloscope signals from the audio source (tape recorder) is a sequence of amplitude, frequency approximation of the sine wave signal with the sound changes. The signal modulated by the modulation circuit is loaded on a 80KHz square wave, its phase (frequency) modulation, and modulation of signal-driven semiconductor laser, the lasers emit a series by the voice modulation of the light pulse. The light pulses in optical transmission through fiber, from fiber-optic light-ended output, the photodiode receives into electrical signals, zoom in, restore. This time can be observed from the oscilloscope to a string of drive signal corresponding to the pulse signal, this pulse signal demodulation by the demodulation circuit, and then restored to near-sinusoidal signal. green laser pointer can help the manufacturer explore the domestic market and oversea market further.
At this time, observed a wide range of audio sources output signal corresponding to the waveform from the oscilloscope. This approximation of the sine wave signal is amplified by the power to drive the speakers, you can hear the sound. Electro-optical properties of semiconductor lasers. The semiconductor laser is the most rapid development in recent years as a laser. Because of its small size, light weight, high efficiency, low cost, has entered the field of human social activities. Therefore, it is very important for the understanding and use of semiconductor lasers. In this study, the semiconductor laser to carry out some basic research, in order to grasp some basic characteristics of the semiconductor laser and use. And quality control of laser pointer should be introduced.
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