A single fiber in the park POL can transmit in both directions, relying on wavelength separation: light of different wavelengths does not interfere with each other. GPON agrees that downlink 1490nm, uplink 1310nm, and 1550nm are reserved for video overlay. If you understand this division of labor, you will have answers to your construction questions.

Why down 1490, up 1310

In the downlink, the OLT broadcasts to all ONUs, and the channel should be wide, and is placed on 1490nm; in the upstream, each room is transmitted in bursts in a time-sharing manner, and is placed on 1310nm, avoiding the downlink main channel. The two wavelengths run toward each other in the same fiber, and a filter is used inside the ONU to separate them. The insertion loss caused by filtering is generally controlled at around 1dB. This is also the reason why single-fiber bidirectional equipment must be divided into A and B ends. If the reverse link is installed in the direction, the link will not work.

What does the superposition position of 1550nm leave?

  • IPTV and surveillance video backhaul: 1550nm and data wavelength division co-fiber, do not occupy the data channel bandwidth.
  • Broadcast and Public Area Audio: One 1550 downlink can be split to many terminals.
  • Overlay margin for the evolution to 10G-PON: Replace the end-side equipment without replacing the optical fiber in the building.

What to check when changing modules and terminals

First check the wavelength and fiber number: likeSFP 2.5G single mode dual fiber 20KM optical moduleSuch a dual-fiber module is only suitable for point-to-point transmission and reception, and cannot be used with single-fiber wavelength division equipment. Then check the pairing direction. For single-fiber transceiver, please refer toGigabit single mode single fiber one optical one electrical fiber optic transceiverpairing usage. Finally, don't skip cleaning. The filter structure is sensitive to dirt. Once the end face is dirty, the loss may increase by several dB.

Wavelength separation makes it possible for one fiber to enter the room; check the pairing and re-measure the optical power. EB-LINK technical support can help confirm the device wavelength specifications (0755-83179002).