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What is an OTDR and its basic working principle

What is an OTDR and its basic working principle?
OTDR is an Optical Time-domain Reflectometer. It is the main devices in optical fiber
measurement. It uses to test detect problems that may exist in fiber links.
OTDR is widely used in carrier backbone networks. By analyzing the measurement
curve, it can quickly detect the fault location of the optical fiber link and the fiber loss.
The working principle is to use a laser light to send a higher power laser or light pulse
to the test fiber. OTDR observes the power of the laser signal from each point on the
fiber and records these results through a trace diagram. It can calculate the distance
by recording the return time and transmission speed.
In the PON (Passive Optical Network) network, especially the complex point-tomultipoint PON ODN (Optical Distribution Network) topology applications, rapid
monitoring, and diagnosis of fiber fault locations is a challenging subject. At present,
optical time-domain reflectometer (OTDR) tools are widely used for monitoring the
fiber network. However, OTDR detection may not be so particularly sensitive to the
attenuation of optical signals at the ends of some ODN branch fibers or ONU fibers.
The application of FTTx terminal splitter to the main cable signal makes the traditional
OTDR fiber optical detection techniques unable to achieve on-off detection. So a costeffective and wavelength selective fiber optic reflector is a basic method of
implementation of optical layer monitoring on the whole length of an FTTx network
from the OLT to the ONT in real-time.
The working principle of the fiber optic reflector is mainly to use Fiber Bragg Grating
(FBG) to reflect the test light pulse sent by OTDR with nearly 100% reflectivity. But the
wavelength of normal passive optical network (PON) will pass with a small attenuation.
The main purpose is to accurately calculate the return loss value of the reflected event
at the end of each ONU branch by detecting whether the reflected OTDR test signal
exists and the intensity of the optical signal. Therefore, it can easy to determine
whether the optical link from the OLT side to the ONU side is normal. By detecting the
reflected signal through OTDR, it can accurately grasp the fiber breakage, loss
anomalies, fault location, and locate the error quickly.
The end-to-end OTDR measurement from the OLT to the ONT is usually difficult
because the splitter brings high losses and complex networks. The application of
optical fiber reflector is a cost-effective solution to help OTDR detection, and is the
best way to realize real-time end-to-end (OLT to ONT) monitoring of optical networks
in FTTx networks.
The optical fiber (FBG) reflector independently developed by HYC has the advantages
of low insertion loss, high reflectivity, and convenient installation. It is widely used in
PON network, OTDR testing, central computer room testing, FTTX and other fields. HYC
offers customized pigtail or adapter type, such as LC, SC, APC/PC and so on.
HYC provides optical passive components OEM/ODM services. We welcome any
inquiry for customized optical devices solutions for optical communication industry,
including fiber optic connectors/adapters, WDM, PLC splitter, MEMS optical switch for
data center, FTTx, Cloud Computing industry, 4G/5G networks .