Hello, everyone!
Today, I would like to share with you an article on FTTH point-to-point (P2P) networks.
Figure 1. Top download rates offered to residential customers
The FTTH-P2P network's architecture is straightforward: the entire connection between the OLT and the ONT (Figure 1) is made up of a single, continuous single-mode fiber, with no splitting or intermediary active equipment, much like a regular telephone network.
There is no pooling of OLT capacity across various subscribers' ONT units. Wavelength division multiplexing (WDM), which uses the following wavelengths, allows for full-duplex, symmetrical transmission with equivalent bit rates in both directions.
– Downstream (to subscriber): 1480–1500 nm (nominal 1490 nm)
– Upstream (from subscriber): 1260–1360 nm (nominal 1310 nm)
A "single-fiber" optical transceiver module, commonly of the SFP type, contains the essential WDM coupler (duplexer). The 1490 nm wavelength (Figure 2) was chosen as a result of the allocation of 1550 nm in all FTTH networks for analog TV distribution.
This was first required because copyright laws in numerous places, including Japan and the United States, required new, costly licensing for digital dissemination of television content, but retransmission in original analog format (PAL or NTSC) was covered by current licenses.
Figure 2. FTTH-P2P network optical connections and wavelengths
Optical transceivers are made in two different versions for OLT and ONU applications.
The primary physical interface for FTTH-P2P networks is 1 Gb/s 1000BASEBX10, with a power budget of 5.5/6.0 dB at 1310/1490 nm and a maximum fiber length of 10 km. Active equipment for FTTH-P2P networks is built on Ethernet standards, and this type of network is known as "active Ethernet." This range corresponds to the maximum length of subscriber loops, and without the use of remote units, the access network can be converted from copper to fiber.
In sparsely inhabited locations, more expensive 1 Gb/s transceivers with increased reach of 20, 40, or 80 kilometers are available. ITU-T Recommendation G.986 also applies to 1 Gb/s FTTH-P2P networks, where the power budget of an OLT-ONT path in the lowest category S is increased to 15 dB while maintaining a 10 kilometer reach.
Although 10 Gb/s SFP Ethernet transceivers are now available, they are still too expensive to be used in ONTs.
However, after the start of mass manufacture of 10G PON equipment in 2016, prices began to plummet.
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