21581 - SCTE Broadband August2022 COMPLETE v1

41 Vol. 44 No. 3 - September 2022 Issue from the industry optical modules with a greater number of lasers and carry part of the transmission at each wavelength. xWDM – systems that multiply possibilities The WDM (Wavelength Division Multiplexing) technology allows us to further increase the capacity of existing optical fibre. To implement a WDM link, we need two complementary inserts, one wavelength per transmission direction. The simplest solution is to use BiDi modules. Transmission in both directions with usage of two different wavelengths is realised in a single fibre. Thus, for example, when a transmitting (TX) module at 1310nm and a receiving (Rx) module at 1550nm is mounted on one side of the link, then an inverse module (Rx 1310 and Tx 1550) must be mounted on the other side. The bit rates on the existing pair of single-mode optical fibres can also be increased by migrating towards CWDM (Coarse Wave Division Multiplexing) technology. A further development in the direction of wavelength multiplication is DWDM (Dense Wave Division Multiplexing). Compared to CWDM, DWDM technology brings a significant reduction in the width of the channel. There are several options here, differing in the width of the channel plan grid: 100GHz, 75GHz, 50GHz and more. The 100GHz grid uses 0.8nm spacing between the channels, which allows us to organise a 48-channel plan. The next step is to use a 50GHz grid and reduce the channel width to 0.4nm. The frequency of 50GHz allows us to use 96 independent transmission channels. Thanks to DWDM technology, the aggregate capacity of the link has increased significantly. The main advantage of DWDM technology is the possibility of a cost-effective and flexible approach to capacity development based on the available pair of single-mode fibres. At the same time, one can use systems with a different mesh and expand them if necessary. Systems using 100GHz can be used simultaneously with 75GHz and 50GHz optical modules. Within one optical fibre it is possible to mix systems with different grids, a technology called ROADM. This allows users to manage their bandwidth more efficiently. The best solution is to choose the width of the channel in relation to the size of the bitrate. Dark fibre solutions present numerous benefits over new links, from cost reductions to scalability and increased transmission capacity. At Salumanus, we have developed effective solutions to help users make the most of their existing dark fibre and optimise their optical networks. For more information, visit www.salumanus.com