It has been a long time that fiber optic system has required two strands of fiber to accomplish full duplex communications—one is for transmitting and the other is for receiving. But the emergence of single strand fiber transmission changes the situation. It seems to be a better alternative for network managers who is with limited fiber capacity and limited budgets. In addition, it is becoming a more and more popular option for new installations. But is it right for you? Take several minutes to read this paper, I think you may have the answer.
Single strand fiber transmission use a single strand of glass (optical fiber) to send data in both directions, namely bidirectional (BiDi) transmission. In recent years, the mainstream single strand fiber transmission technology is based on two wavelengths traveling in opposite directions (also called TW BiDi transmission). This technology is achieved via wavelength division multiplexing (WDM) couplers, also known as diplexers, which combine and separate data transmitted over a single fiber based on the wavelengths of the light. Generally, this WDM coupler is integrated into a standard interface optical transceiver module.
Actually, in addition to the two wavelengths BiDi transmission, the single wavelength (SW) BiDi solution was hot when the fiber resource was rare and 1550nm DFB laser was expensive. It is based on single wavelength directional coupler technologies which allows the same wavelength (e.g., 1310 nm for up to 50 km or 1550 nm for longer distances) travels in Tx and Rx direction—two signals are coupled into a single fiber strand with a directional coupler (splitter-combiner). Then the coupler identifies the direction of the two signals (ingress or egress) and separates or combines them. This solution is normally very reliable and cost effective for gigabit applications since they need to deploy only one kind of transceivers at 1550nm (or 1310nm). However, the SW BiDi implementation could not support high bit rate because of the reflection noise.
Single strand fiber solution with its benefits and recognized potential is becoming more and more widely used in communication systems of optical transport networks, access networks, wireless backhaul networks, and private transmission network, meeting the customers’ needs and making every effort to save in the capital expenditure (CAPEX) and the operational expenditure (OPEX).
Increases Network Capacity—Working with single strand fiber, the capacity of the fiber can be increased double by simultaneously operating at more than one wavelength, transmitting and receiving on a single strand. For instance, if you have a six-strand cable, then you are able to gain all six lines for communication. But you could only gain half of lines for communication if you use the traditional method of transmitting and receiving on separate fibers.
Increases Reliability—Single strand fiber solution is less susceptible to connection errors because there are fewer connections or end points in the network. In addition, customer can also choose to use single fiber to decrease redundancy in the network.
Overall Cost Saving—Costs including fiber optic cabling, labor and material involved in terminating the endpoints etc., can be reduced by working with single fiber solution. Decreasing the total amount of fiber results in a reduction of overall labor costs. Construction costs are avoided since you are increasing the capacity of existing fiber versus installing additional fiber. Additionally, reducing the number of terminated fiber strands by half means fewer patch cords and patch panel ports, which results in a significant cost reduction.
However, as the saying goes, every coin has two sides. There are some limitation of single strand fiber solution as well. We can’t get the same range/distance out single fiber as dual fiber. And at present, types of transceiver optics available for single fiber are limited and cost more. This is why though single fiber transmission is with so many benefits, it still can not replace the dual fiber transmission in deployment. Thus, you should be clear about the limitation of single strand fiber solution when you are ready to adopt it.
To achieve single strand fiber transmission, a variety of single strand fiber optics are required which ensure users to simultaneously send and receive data on one strand fiber. Here, several types of common single strand components are introduced.
BiDi transceiver, also called WDM transceiver, is a type of optical transceiver module designed based on WDM bi-directional transmission technology. Unlike the conventional optical modules, it has only one optical port which uses an integral WDM coupler to transmit and receive signals over a single strand fiber. In general, it is used in pairs. For example, if you use a BiDi transceiver which has a receiving wavelength of 1550 nm and a transmit wavelength of 1310 nm, you should use its matching module which has a receiving wavelength of 1310 nm and a transmit wavelength of 1550 nm. At present, the BiDi SFP (Small Form-Factor Pluggable) optics are common. BiDi 10Gbase SFP+ (Enhanced Small Form-Factor Pluggable) optics and 40Gbase QSFP (Quad Small Form-Factor Pluggable) optics are only supplies by several vendors.
Simplex fiber patch cables are used to accomplish connectivity between two BiDi transceivers. It is usually designed with single-mode fiber and pre-terminated with LC connectors to fit the optical interface of the BiDi SFP/ SFP+ optics and operating wavelength.
Single strand fiber to Ethernet converter which enables connections of UTP (Unshielded Twisted pair) copper-based Ethernet equipment over a single strand fiber optic link is ideal for fiber to subscriber service providers, enterprise LAN networks, or just about any application where there are limits on available fiber. Using the converters can help network administrators take advantage of the cost savings in both material and labour associated with single strand fiber and double fiber capacity without pulling new cable.
Simplex BiDi WDM Mux/DeMux (multiplexer/de-multiplexer) is used to combine and separate wavelengths as the conventional WDM Mux/DeMux, but designed for use in single strand fiber transmission. In general, they should be used in pairs, and the Mux/DeMux ports for specific wavelengths must be oppsite. According to the system types, it can divided into CWDM (Coarse Wavelength Division Multiplexing) BiDi Mux/DeMux and DWDM (Dense Wavelength Division Multiplexing) BiDi Mux/DeMux.
There are so many other components associated with single strand fiber solution, such as simplex PLC (Planar Lightwave Circuit) splitters, OADM (Optical Add Drop Multiplexer) and other simplex fiber products, which are not listed here in detail.
Via a short description, we have introduced the single fiber transmission technology, the benefits and limitation of single strand fiber solution, as well as the common components used in single fiber transmission system. There’s no denying that single strand fiber solution has a huge advantage on helping users save cost and increase network capacity. But because of its limitations, it is still as not universal as dual fiber solution. Meanwhile, when deploying single strand fiber solution, various of single strand fiber optic components are required. So, after reading the whole content, do you have the answer for the question mentioned in the beginning? If you still worry about the cost of deploying single strand fiber solution, Fiberstore’s single fiber solution may be an ideal choice for you as it is comprehensive and cost-effective.
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