 Baek, Y.-S., Oh, K.-R., Multiwavelength lasers for WDM-PON optical line terminal source by silica planar lightwave circuit hybrid inte- gration, IEEE Photonics Technology Letters, 19(20), 1622-1624 (2007). Telecommunication Networks 32. Lambert, D. J. H., Joyner, C. H., Rossi, J., Kish, F. A., Nagarajan, R., Grubb, S., Van Leeuwan, F., Kato, M., et al., Large-scale photonic integrated circuits used for ultra long haul transmission, The 20th Annual Meeting of the IEEE Lasers and Electro-Optics Society, LEOS 2007, Lake Buena Vista, FL, pp. 778-77, 2007. Chang, Y. (Frank), First demonstration of a fast response/locking burst-mode physical lay- erchipset for emerging 10G PON standards, European Conference on Optical Communications- ECOC 2009, Vienna, Austria, p. 629, 2009. Appendix A: SDH/SONET Signaling In this appendix, we will specify the working of SDH/SONET signaling looking in detail at the structure of the frame at the different layers. This analysis is doubly useful, both as an example of the completeness and complexity of the signaling structure of a carrier class network and for practical reasons. As a matter of fact, the SDH/SONET framing is also frequently used in other kinds of equipment for the sake of compatibility and because all the needed hardware is available. We will concentrate on SDH, specifying when needed the differences with SONET. All the elements reported in this appendix, including the figures, have their origin in SDH/SONET standards. Thus, we refer the reader to the relevant bibliography of Chapter 3 for the original documents. A.1 SDH Frame Structure Each SDH frame starts with framing bytes, which enable the equipment receiving the SDH data stream to identify the beginning of each frame. The location of the other bytes within this frame structure is determined by its position relative to the framing byte. The organization of the frame can be easily understood by representing the frame struc- ture as a rectangle comprising of boxes arranged in N rows and M columns, where each box carrie