Uploaded by HYC Co., Ltd

How does FBG (Fiber Bragg Grating) Optical Reflector work

How does FBG (Fiber Bragg Grating) Optical Reflector work?
FBG fiber optic reflector, also known as Fiber Bragg Grating Filter, is usually installed on the front
end of the ONU. Combined with OTDR equipment, it can realize the point-to-point (PTP) or
point-to-multipoint (PTMP) network monitoring of optical link, which can reflect the network
abnormality quickly and accurately.
What is FBG? FBG is Fiber Bragg Grating. A fiber grating is a type of diffraction grating. Fiber
Bragg Gratings (FBG) is a simple and low-cost way to build a grating into a specific wavelength
range of fiber. When broad-spectrum light is incident on the fiber with built-in grating, the
wavelength matching the grating will be reflected back to the input end, and the rest of the light
will be passed through to the other end. Fiber gratings have the characteristics of small size, good
wavelength selectivity, good compatibility, etc. The manufacturing process for fiber gratings is
mature, with good practicality and low cost, they are widely used in the field of communication
and sensing and is also ideal important device in optical network.
The FBG optical reflector utilizes the wavelength selectivity of the fiber grating, and the fiber
grating is embedded in the adapter. It can be conveniently installed on the front end of an optical
network (ONU), and it can quickly and accurately implement optical network fault detection with
the help of an optical time domain reflector (OTDR). Due to the excellent wavelength selection
characteristics of fiber gratings, anti-electromagnetic interference, the center wavelength drift is
small with the change of external temperature, and when the optical network coverage and
depth continue to increase, the entire optical network fault point can be detected quickly and
With the application of optical splitters in passive optical network (PON) networks, the
complexity of the ODN network deployment environment has been increased. The splitters at the
end of the FTTx will split the trunk optical signals and increase the difficulty to identify
attenuation events on ODN branch fibers. The application of fiber grating reflector is a
wavelength selective reflector based on this environment, which aims to improve the fast and
accurate detection of optical link failure events by OTDR.
The fiber optic reflector is usually installed on the ONU side. The OTDR detects the intensity of
the optical signal reflected by this reflector and compares the return loss between the normal
line and the failed link to determine whether the optical fiber in the link is damaged or not. The
normal PON system working wavelength does not meet the reflector conditions then will pass
through the reflector with a small attenuation. While the reflector achieves the monitoring
function, but without disturbing the transmit. 1650nm fiber grating reflector, the grating
reflection wavelength is 1645 ~ 1650nm. The optical signal in this Bragg wavelength range will
return along the input path, and all other wavelengths of light (1260 ~ 1625nm) can pass through.
If the input optical signal segment can detect the fiber grating reflection peaks in this band, it can
be judged that the transmission path is normal. Otherwise, it is abnormal.
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 fiber optic reflector is a
cost-effective solution to help OTDR detection, and it is the best way to implement real-time
end-to-end (OLT to ONT) monitoring of optical networks in FTTx networks.
HYC's self-developed FBG fiber optic reflector has the advantages of low insertion loss, high
reflectivity, and easy installation. It is widely used in PON networks, OTDR testing, central
computer room testing, FTTX and other fields. It can be customized as special pigtail or adapter
type, and the connector interface is LC, SC APC / PC.
About HYC
HYC Co., Ltd is a leading OEM / ODM and solution provider of optical passive devices in the
industry, focusing on R&D, design, manufacturing, sales and service of passive devices for optical
communication. HYC has an international R&D and operation team, advanced automated
production and testing equipment, and an information-based lean operation system, with
excellent design and development capabilities, large-scale organization and production capacity,
quality control capabilities, providing high stability, cost-effective, and leading technology