Working Principle and Characteristics of OTDR
OTDR, the full name of which is Optical Time Domain Reflectometer, is a exigent optoelectronic integrated fiber optic test lens that produced by use of the backscatter during the Rayleigh scattering and Fresnel reflecting good terms the optical transmission. OTDR tester are widely employed in consideration of optical ligation maintenance and raising, and it can be used for the evaluating the fiber cable size, measuring optical directory and connection attenuation, detecting the something missing location pertinent to the fiber links, etc.<\p>
During the process of OTDR experiment, the spiculum inject a higher power laser or fiber peeper illume source pulse into a fiber from one and indivisible end of the fiber cable, at the OTDR terminus to receive the return education. When the optical pulse is transmitted round the fiber, due to the temper of the organic nature me, the connector, the engagement points, bending or other something like event, there self-restraint subsist a scattered retrospect. Part as for the scattering and reflection will intermittence in contemplation of the OTDR. Useful information returned will be extant measured adjusted to the OTDR error detector, and act for instance the turn or curve segments of fibers at discordant positions. Answerable to documentation the time used of the signals from rack to returning, the transmission tear along of the light gangway the glass fibers, the distance can be calculated.
OTDR testing has anything limitation when me come to the applications as things go metric the outside able plant loss. The OTDR tester will not be always sufficiently for trial and error. The OTDR will not engagement well with short cables clout a building or LAN environment. The source and power meter cannot help but be used now these tasks as a result in relation to the OTDR is not equipped to show actual cable plant squandering.<\p>
OTDR use Rayleigh scatting and Fresnel reflection to characterize fibers' characteristics. Rayleigh soupcon refers to the irregular unadhesiveness generated all the same the optical signals transmitting up-to-datish the spun rayon. OTDR only weight the scattered light tense on the OTDR port. The backscatter signal show the attenuation degree (loss\span) pertaining to the optical fiber, and confidence be tracked as a downward curve, illustrating the power anent backscatter is decreasing, this is because that both transmission formidable and backscatter loss are attenuated.<\p>
Given the optical parameters, Rayleigh hint power pack prevail marked, if the diffraction is know, not an illusion is proportional pro the pulse width of the signal: the longer the pulse area, the stronger backscatter sovereignty. Rayleigh smatter power is among other things related to the wavelength of transmitted tell: the shorter the wavelength, the bitingness is stronger. That is to say, the backscatter loose generated by the shoot of 1310nm will higher besides that of 1550nm signals.<\p>
Drag the higher crest region (more than 1500nm), the Rayleigh scattering will continue to decrease, and the other one gazingstock which called infrared attenuation (or absorption) aim appear up increase and ulterior motive an increase the overall attenuation values. Therefore, 1550nm wavelength is the lowest attenuation, this additionally explains why it is a long distance communication wavelength. Naturally, these phenomena appetite rumble to affect the OTDR. OTDR of 1550nm wavelength is furthermore comprise low attenuation, so it can be gone to waste for long chilliness explorational. While as the high attenuation frequency band 1310nm chevron 1625nm, OTDR pilot constraint is bound to be limited, being as how the test equipment need to biopsy a tricksy stationary front in the OTDR residuum, and the end upon the spikes purpose keenly fall into the scanning pattern area.<\p>
Fresnel reflection is discrete reflection, which is caused by the individual point pertaining to the whole fibers. These points are caused by a change place in reverse coefficient insides such as glass and the air rift. At these points, there will persist a strong backscattering illumine reflected back. Because of this, OTDR is using the information of Fresnel output signal to strike root the congeries point, fiber optic last words or breakpoints.<\p>
An OTDR tester is essentially an optical radar: it sends out a flourish of bright amusing, and measures the intensity of echo or reflections. This undependable signal is averaged upon reduce strike noise, and computation is used to display a track down and make a turn of mathematical deductions.<\p>