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How to Use Optical Splitter for FTTH Network Spectral Construction?

- Jan 26, 2018 -

Optical splitters play an important role in PON (Passive Optical Network) in Fiber to the Home (FTTH), which makes it possible for multiple users to share one PON interface.Optical splitters are generally installed between an optical line terminal (OLT) and an optical network terminal (ONT) of a PON. How to use the optical splitter to split the FTTH network?This tutorial will explore this issue in detail.

Before starting to discuss the splitting construction of FTTH network, it is necessary to understand different optical splitters.Currently there are two common optical splitter PLC splitter and FBT optical splitter, the following table shows the contrast between the two optical splitters:


Wavelength Range

Splitting Ratio


Wavelength Sensitivity


PLC Splitter


equally distributed




FBT Optical Splitter

single/double /three windows

Uneven/equally distributed

  Large when multiplexed



the demand for the optical splitter optical splitter is getting higher and higher.Therefore, PLC optical splitter with its advantages such as many branches and uniform light becomes more popular optical splitter in FTTH applications. 

FTTH network of the building

 PON is the foundation of FTTH network, and optical splitter is an important part of PON network.The PON network has two levels of splitting: one-level splitting and two-level splitting. The first splitting mode means that the optical splitter is concentrated in the fiber distribution box and directly connected to the central office OLT via a single optical fiber and the other end passes Multiple optical fibers are connected to multiple ONTs on the customer premises. The splitting ratio of the optical splitter in the first splitter is usually 1:32 or 1:64.

The two-stage splitting method means that two optical splitters are connected between the OLT and the ONU in a cascaded manner.This spectroscopy has two points: a first-order and second-class points. A first-class points are usually located near the central office end, the general use of 1 × 4 optical splitter; second-class points are generally installed in the client (such as the corridor), a number of optical splitter, the general use of 1 × 8 light splitter.

The first-class optical splitting method (optical splitter centralized distribution) has the advantages of high flexibility, low operation cost and easy maintenance. The second-class optical splitting method (optical splitting cascade distribution) has features like a faster return on investment and a lower initial input cost .Therefore, the first-class method is usually suitable for users with concentrated urban centers or towns. The second-class method is usually used in sparsely populated villages.

Fractional Ratio Design of FTTH Network

The 1: N (N = 2-64) or 2: N (N = 2-64) optical splitter is a commonly used optical splitter in PON, where "N" refers to the number of output ports.Optical splitters with different splitting ratios will also play different roles in the FTTH network.For example, as mentioned above, a 1 × 32 optical splitter or a 1 × 64 optical splitter is suitable for the first-class optical splitter. A 1 × 4 optical splitter or a 1 × 8 optical splitter is suitable for the second-class optical splitter roads.In addition, a 1 × 32 optical splitter (transmission distance is usually 20 km) is recommended if the distance between the OLT and the ONU is long, and 1 × 64 splitter if the distance between the OLT and the ONU is short .

To sum up, the first-class and second-class spectroscopy methods have their own advantages and disadvantages, we should select the appropriate spectroscopy according to the specific circumstances.As for the optical splitter than the splitting ratio, the longer the transmission distance, the optical splitter should be selected less the number of optical splitters.

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