# Photonic Integrated Circuits for NGPON2 ONU Transceivers (Invited)
## 4 PIC for Next-Generation PON
### Control Complexity, Power Dissipation and Form Factor  
The different PON standards and technologies have their own requirements in terms of complexity control, especially for tunable devices. When wavelength control is not essential, simpler actuation systems with lower power are required [88]. Nonetheless, once the wavelength spectrum becomes more crowded, the options have to be restricted and the requirements for more complex control increase [7]. A summary of the technology and expected power for its optoelectronic interfaces versus the complexity and requirements for a certain interface is depicted in Figure 8. A general sweep, from low data rate with large wavelength range and short-reach to higher data rate with tighter wavelength range and longer reaches, are also presented in the Figure 8. Additionally, the technologies with an approximate relative power requirement classification (from low to high power) are also identified. The x-axis represents the optical requirements, ranging from low data rate and short-reach to long-reach DWDM and high data rate. The red arrows describe the complexity steps from the system requirements. Potential form factor solutions able to cope with the required power dissipation are also presented in the far right of Figure 8. Technology evolution poses increasing challenges in the control complexity and required power. As the demanded power grows, a change in the form factor is needed. Form factors have two major characteristics: minimum volume and maximum dissipated power [89]. An approximate chart of the average pricing for GPON, XGSPON, and NGPON2 evolution versus time is presented in Figure 9. GPON faced a strong price drop with its increased manufacturability, pushed by the worldwide broad adoption of the technology by the operators. XGSPON is following the same steps, which for the user can be the motto to have 10 Gbit solutions sooner. Technically, XGSPON generically adopted the physical layer characteristics of IEEE 802.3 av 10 GEPON systems, e.g., differing in the burst mode timing requirements [70; 78]. Moreover, to jump-start the market, initial implementations of XGSPON systems relaxed the timing requirements to fully adopt 10 GEPON standards [70]. With this rapid price erosion model, the profit margins in the supply chain depreciate very fast. As NGPON2 is based on the limited tunability of DWDM lasers and receivers, it poses some challenges for its adoption by manufacturers, vendors, and operators. This fact has delayed its deployment process. NGPON2 technology differs from the traditional model since it goes out of the O-band, making the laser control and manufacturability more stringent. Thus, it results in a potentially slower cost reduction and more sustainability from the supply chain point of view [7]. Figure 8: Diagram of requirements in terms of control, complexity, and power for different technologies. The indicative pricing evolution of the traditional bulk type BOSA for the three technologies is depicted in Figure 9. Early, broad and late adoption notes refer to perception and predictions estimated by the authors given the present standing of the technology. Pricing is indicative and may not represent all realities/contexts, and is based on, per vendor and per order, 100 pieces at the early adoption stage, 100k pieces at broad adoption, and 1M pieces at late adoption stages, see Figure 9.  
A reduction in physical volume, number of sub-assemblies, and calibration steps are expected with the migration to PICs. These steps may greatly reduce the price of the subassemblies based on PICs when compared with traditional bulk BOSA [7, 8]. As identified above, by having upstream/downstream on approximately the same wavelength band, NGPON2 can be a great applicant for monolithic PIC. In such a case, ONU and OLT can coexist in the same PIC platform without further processing.