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Passive Optical Network standards have been formulated by International Telecommunications Union (ITU) in order to streamline the specifications so that end users can use products from multiple vendors complying with ITU recommendations. Passive optical network architecture has been accepted worldwide for quick and effective deployment of optical fiber based broadband technologies. Ever increasing bandwidth requirements have urged ITU to draft Next generation Passive optical network standards.

NG-PON2 (Next-Generation Passive Optical Network 2) is a 2015 telecommunications network standard for a passive optical network (PON), developed by ITU. NG-PON2 offers 10 Gbps to the subscriber – Yes, the next generation really needs that bandwidth. NG-PON2 standard details an architecture capable of total network throughput of 40 Gbps, corresponding to up to 10 Gbps symmetric upstream/downstream speeds available at each subscriber.

ITU-T proposed PON architecture for the Access-Distribution-Drop sections of the Fiber to the X network in order to avoid hassle-free and maintenance free infrastructure as far as possible. In a PON system, the active equipment is limited to the Central office and subscriber premise, that is, at the start end and the final end of the networks. Active equipment is located at these two ends and there is no equipment to be powered in the intermediate section.

PONs are managed by passive optics such as unpowered splitters and filters, offering high reliability and low cost compared to active networks. At the customer end, the PON data stream is usually converted and distributed through Ethernet and/or Wi-Fi. ONU/ONT that is embedded with wireless routers is available these days. At home, I use a separate Wireless router.

Existing fiber optic cables are able to carry the required 40G or 100G and beyond and hence these fibers are compatible with NG-PON2. What we need to replace is the transmission equipment and ONU/ONT (Optical Network Unit/Optical Network Terminal). Only active equipment needs replacement to update to the NG-PON2. Both active filters and tunable lasers are used in the Optical Network Terminal.

How NG-PON2 Works?

The wavelength range used for NG PON2 for upstream direction is from 1524nm to 1544nm, which is a band of 20nm. On the other hand, the downstream wavelengths are 1596 nm to 1602 nm, which is a 6nm band.

From the transmitter side, the light signals having different wavelengths from four optical line terminal equipment are multiplexed using a wavelength multiplexer and send through an optical fiber. At the customer’s end, the optical network unit is dynamically assigned to just one optical line terminal equipment. The Optical network unit communicates with tunable laser in the upstream direction and active filters in the downstream direction.

A tunable laser’s wavelength of operation can be altered in a controlled manner. An active filter is an analog circuit having an electronic filter using active components.