3 Types of optical networks, their architectures and basic parameters (OTH, FFTx)
3.2 Access Networks

OAN - Optical Access Networks

- Simplex transmission with SDM (Space Division Multiplexing), for each direction of transmission there is one fibre.
- Duplex transmission with WDM (Wavelength Division Multiplexing), signals are transmitted in one fibre, one direction of transmission is in the area of 1310 nm, the opposite direction is in the area of 1550 nm.
- Duplex transmission with FDM (Frequency Division Multiplexing), signals is transmitted in one fibre, directions of transmission are around one wavelength and they are separated by frequency spacing.
  - Short Haul – max. attenuation 16.5 dB in CWDM, min. attenuation 5 dB, reach 30 – 50 km for P2P.
  - Long Haul – max. attenuation 25.5 dB in CWDM, min. attenuation 14 dB, reach 50 – 80 km for P2P.
  - Typical attenuation of CWDM network elements is 3.5 – 7.5 dB. EDFA can extend the reach.

## Active Optical Networks

AON - Active Optical Networks. It employs active network components to interconnect network elements, such as amplifiers.

However, there are Reach Extended PON (REPON), where using an Erbium Doped Fibre Amplifier (EDFA) is permitted.

## Passive Optical Networks

PON - Passive Optical Networks: multipoint networks that can be classified according to the functionality of components splitting optical signals. They can be splitters or Array Waveguide Gratings (AWG). In WDM, signals can be split by optical filtering by using so-called add-drop multiplexors.

- BPON - Broadband PON - 622.04 Mbps was added, two fibres are used for both directions of transmission or there is one fibre combined with WDM: 1260 - 1360 nm – uplink, 1480 - 1500 nm – downlink. Optionally 1539 - 1565 nm – is for 16 + 16 DWDM channels with the 0.8 nm channel spacing, 1550 - 1560 nm – is for distribution of video.
- GPON - Gigabit PON - ITU-T G.984 –with nominal rate of 1.244 and 2.488 Gbps (max. 128 users).
- EPON - Ethernet PON. Optical connection: P2MP. 1.25 Gbps in accordance with 1000BASE-PX. For upstream (from user to provider), the wavelength of 1310 nm is used, for downstream, it is 1490 nm. Type 1 – max. reach is 10 km. Type 2 – max. reach 20 km.