Overview

Around the world, bandwidth is in high demand, the more the better. Fiber Optics has been delivering large bandwidth to end users for the last decade. In Fiber to the Home systems (FTTH), data is delivered from central switching offices (COs) to the home via a Passive Optical Network (PON), composed of fiber cables and passive optical splitters.  In the central office, data is placed onto the fiber through a transceiver known as an Optical Line Termination (OLT), and received at the home in an Optical Network Unit (ONU). In a typical FTTH network configuration, the data from a single OLT is split into 32 separate fibers; the OLT transmits data to every ONU at the same time and the ONU uses the MAC address to tell which data to receive. But, when the ONU transmits data, only one can talk at the same time since all of the ONU data is received at the OLT. The way this works is by Time Division Multiplexing (TDM), where the ONU is assigned a time slot where it can transmit data and the OLT receives only that data. Because of the way TDM operates, the efficiency of the TDM determines the capacity of the network. That is, the longer it takes to switch from one ONU to the next, the lower the total available data. This places very stringent demands on the “dead zone” between transmission windows.  Therefore, the performance of OLT receivers is more stringent than the basic data rate would imply, since they must turn on and off very quickly as well as simply receiving data. Further, OLTs manage a very large range of signal strengths since the distance from a Central Office (CO) to subscribers homes can vary from 0 to 20 kilometers. Furthermore, a higher performance OLT transmitter can not only reduce the need for high performance ONUs, but also enable handling unexpected higher losses in the network. In turn this reduces the total network cost and it improves the network resiliency. Today NeoPhotonics is a market leader for high performance OLTs that provide high transmitter power along with best-in-class “burst mode” receiver sensitivity by utilizing proprietary burst mode trans-impedance amplifiers (TIA). NeoPhotonics further offers higher speed next-generation PON (NGPON) products including 10G/10G symmetrical ONUs for NGPON applications.

For the wireless back-haul and enterprise networking environment, where fibers are scarce and where it is extremely expensive to deploy new fibers to existing lines, a Bi-Directional (BiDi) transceiver offers a unique way to reduce the need for fibers by half while maintaining the same data throughput as that of a conventional transceiver. While a conventional transceiver needs a pair of fibers to transmit and receive data, a BiDi transceiver uses Wavelength Division Multiplexing (WDM) couplers to combine and separate two different wavelengths to transmit and receive data on only one fiber. Thus to work effectively, BiDi transceivers always have to work in pairs, with their WDM coupler tuned to the expected wavelength of the transmitter and receiver that they will be transmitting data from or to. Along with fiber scarcity, in wireless back haul and enterprise environments, often equipment space is limited. The port density of network equipment can be doubled by incorporating two BiDi transceivers into one SFP module using a NeoPhotonics Compact SFP (C-SFP) module. NeoPhotonics is a market leader for both BiDi transceivers and C-SFP transceivers. Offering a range of BiDi transceivers with data rate up to 10Gbps and distances or reach up to 40KM. NeoPhotonics is also a founding member of the C-SFP MSA and offers a range of C-SFP products with data rates up to 2.5Gbps and with distances or reach up to 20KM.