Enabling GPON for 5G ?

The GPON evolution has initiated enhanced photonic integrated circuits that present a cost-effective alternative to data transmission. A photonic integrated circuits has numerous advantages over the traditional optical sub-assemblies. For instance, considering the occupied volume, the photonic integrated circuits allow a very dense architecture in a small area, passing also by the optical losses; however, the losses in the optical sub-assemblies are higher because of the internal free-space alignment between each optical component.

With photonic integrated circuits technology, a number of optical components such as amplifiers, detectors, lasers, modulators, etc. can be integrated-merged on a single chip.

Therefore, it helps in optical system design simplification, system reliability enhancement, as well as significant power consumption and space reduction. In addition, there can be considerable reduction in the amount of OEO converters required for the system implementation. This subsequently results in the total network cost reduction.

Also, other notable advantages of the photonic integrated circuits compared with the optical sub-assemblies are lower power consumption, lower footprint, and cost-effectiveness. Therefore, photonic integrated circuits have the capability of permitting flexible and high data rate solutions.

By the system realization, I propose three different architectures: the ONU architecture, the OLT architecture, and the architecture that can perform both functions just on hardware selection.

 ONU transceiver architecture

The ONU transceiver architecture is a very simple structure regarding the optical setup, but the electrical control is very tough, mostly because of the tunability (both on the transmitter and on the receiver). Here is one tunable laser. The laser can be tuned by temperature and can be directly or externally modulated (the latter would also need a modulator after the laser). On the receiver part, there is an optical band-pass filter which has to be tunable to allow one of the downstream channels and cut the rest of the spectrum. The tunable band-pass filter is followed by an optical receiver.

OLT transceiver architecture

The OLT is not tunable, both transmitter and receiver should work on the same fixed wavelength pair. Consequently, four pairs of optical devices will be needed. Since it is very difficult to encapsulate everything on the same transceiver, the solution that is being followed commercially is having four different transceivers, one for each wavelength pair, and the wavelength multiplexer (WM) device is external. This WM should, in each port, allow one wavelength pair, meaning that in each port, it should pass only one downstream and the respective upstream channel.

OLT/ONU transmission architecture

The architectures are the basic ones to have functional devices for PON2. But taking advantage of photonic integration, it is possible to develop a much more complex circuit with more functionalities, which is being presented next. The block diagram of an architecture that can be used both as ONU and OLT. This helps in exploiting the advantage of both functionalities.

This purpose (OLT or ONU) to be served can be achieved just by hardware selection. This proposed architecture fits inside a indium phosphide photonic integrated circuits.

Conclusion

The 5G based system is a promising solution for attending to the growing concerns about the traffic pressure on the network. Also, the envisaged massive number of deployment scenarios and use cases to be supported brings about high-bandwidth and low-latency requirements for the 5G networks. The small-cell-based C-RAN approach can efficiently attend to the associated ultradense deployment. However, the C-RAN-based approach imposes stringent requirements regarding jitter, bandwidth, and latency for the mobile transport networks. In this book chapter, we have presented wired and wireless transport solutions that are capable of addressing the C-RAN-based stringent requirements and, consequently, the 5G mobile transport network demands. Furthermore, owing to its significant and inherent advantages for the 5G and beyond networks, we have focused on the PON2 system