What is a Passive Optical Network?

Passive Optical Network (PON) is a pure media network that avoids electromagnetic interference and lightning effects from external equipment, reduces the failure rate of lines and external equipment, improves system reliability, and saves maintenance costs. It is a technology that the telecommunications maintenance department has long expected.

At present, PON is the most attractive technology to solve the "last mile" of access network and realize FTTx. The so-called "passive" means that the ODN does not contain any active electronic devices and power supplies, and is composed of passive devices such as optical splitters. Therefore, the cost of management and maintenance is low. The most advantageous aspect in the development of the Internet.

PON can be divided into PSPON (power division passive optical network) and WDMPON (wavelength division multiplexing passive optical network) according to the signal distribution method. APON, BPON, EPON, and GPON all belong to PSPON. PSPON uses a star coupler to split, and uplink / downlink transmission uses TDMA / TDM to achieve channel bandwidth sharing. The splitter distributes the signals sent by the OLT to each ONU through power distribution . WDMPON technology

There are currently many ways to construct a multi-wavelength light source. One approach is to choose a set of wavelengths that are close, discrete, and tunable

In a WDMPON system,

ONU light source selection principles are easy to install and maintain, low cost, and the spectrum should work over the entire wavelength range of WDMPON. There are currently 4 types of ONU light sources.

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1. Network planning for PON equipment-OLT deployment. In the initial stage of xPON construction, centralized settings should be adopted, and OLT nodes should be set at the transmission convergence nodes to cover scattered users in a certain area. In the mature period of xPON application, the principle of decentralized settings should be adopted, and the OLT should be set up in a wired access or wireless access point room with better conditions, and the transition to the access network access and wireless access point will be unified and gradually realized Comprehensive utilization of basic resources. Adopt large-capacity OLT equipment, make full use of the distance advantage of optical access, reduce local offices, and reduce maintenance costs ^[5] .

2. Network planning of PON equipment-deployment of optical splitters. Optical splitter splitting: At present, PON can adopt two-level optical splitting to ensure flexible deployment and full use of ports. When the user penetration rate increases, adjust the second-level optical splitting to first-level optical splitting. For the current access to the PON network, a first-level splitting Beam splitting, try not to exceed two levels of beam splitting. When the user scale is small, the beam splitters should be set centrally; when the user scale is large, the beam splitters can be appropriately dispersed to be as close to the user as possible. Location of the optical splitter: The optical splitter can be placed in the transfer box, the residential equipment room, the corridor, and the weak current well according to the actual situation of the project ^[5] .

3. Network planning of PON equipment-deployment of ONU. When constructing a PON network to implement an access network / FTTB, it is advisable to use equipment with a built-in voice module as far as possible to achieve integrated service access. The ONU should be set according to the application mode and service requirements of the FTTx network. For access network applications, the ONU should be installed in the user's home as much as possible, and should not be installed in the doorway or corridor. For ordinary public users, the ONU can be set in the smart box of the user terminal to provide protection, or placed on the desktop (using an optical fiber information socket). For FTTB applications, you can choose to place ONUs in different places such as building corridors or in-shaft cabinets, outdoor light transfer boxes, etc. ONU adopts local power supply in principle, and does not use remote power supply as much as possible. In order to ensure the normal development of voice services during power failure, backup power can be provided according to the provided battery module ^[5] .

4. Network planning of PON equipment-network management. Centralize the construction of the manufacturer's network management and open the northbound interface for easy access to the integrated network management of transmission.