Traffic Analysis Point (TAP) For Real-time Network Monitoring

TAP stands for Traffic Analysis Point, which is designed to provide real-time monitoring and reporting between two or more points within a fiber-optic network.

TAP has two distinct types, active TAP and passive TAP. Passive TAP is a purely passive device which does not require power. It is much more common in enterprise data centers and is used for creating network visibility and enhancing network security. Thin-film filter (TFF) technology has become a popular TAP manufacturing technology due to its reflected and transmitted light with low performance and high insertion loss.

The tap is positioned in the cabling system, which allows network traffic to flow from ports A to B, and B to A without interruption, but provides the exact duplicate of the signal on the network link to the monitoring port. There are two points. Firstly, it won’t cause any disruption to the normal network activity. It places no burden on the network, and don’t contribute to dropped packets. Secondly, it creates an exact copy of both sides of the traffic flow to the monitoring ports for data analysis. So the most accurate real-time monitoring and analysis of the network can be achieved by this TAP.

Different split ratios are generally available from 1% up to 50% distribution as needed for the particular installation circumstances. For a 70/30 TAP, you can split 30 is for monitoring port. The ratios are pre-determined and usually depends on the distance of network nodes and monitor ports. The important point is to find the split ratio at which both the primary passthrough link and the monitor link can both function reliably.

What’re the features of TAP?
1. Require no extra powering. When the power to the device is lost, it is impossible to be a point of failure in the network link.
2. It is an effective, and cost-efficient way for real-time network monitoring.
3. It passes all link traffic for monitoring. Even corrupt data will not be rejected, so users can see everything in real-time.
4. It won’t affect network operation. The monitoring is done without adding any disruptions to the network.
5. It is highly reliable and requires no maintenance.

When networks become larger and more complex, monitoring for performance and security is no longer optional, it becomes critical. TAP provides a simple and powerful way to monitor optical networks.

How to Use Fiber Optic Reflector for PON Monitoring

In the PON (Passive Optical Network) network, especially the complex point-to-multipoint PON ODN (Optical Distribution Network) topology applications, rapid monitoring, and diagnosis of fiber fault locations is a challenging subject. At present, optical time-domain reflectometer (OTDR) tools are widely used for monitoring the fiber network. However, OTDR detection may not be so particularly sensitive to the attenuation of optical signals at the ends of some ODN branch fibers or ONU fibers. The application of FTTx terminal splitter to the main cable signal makes the traditional OTDR fiber optical detection techniques unable to achieve on-off detection. So a cost-effective and wavelength selective fiber optic reflector is a basic method of implementation of optical layer monitoring on the whole length of an FTTx network from the OLT to the ONT in real-time.

The working principle of the fiber optic reflector is mainly to use Fiber Bragg Grating (FBG) to reflect the test light pulse sent by OTDR with nearly 100% reflectivity. But the wavelength of normal passive optical network (PON) will pass with a small attenuation. The main purpose is to accurately calculate the return loss value of the reflected event at the end of each ONU branch by detecting whether the reflected OTDR test signal exists and the intensity of the optical signal. Therefore, it can easy to determine whether the optical link from the OLT side to the ONU side is normal. By detecting the reflected signal through OTDR, it can accurately grasp the fiber breakage, loss anomalies, fault location, and locate the error quickly.

By deploying fiber optic reflectors at the different positions to monitoring different ODN sections, the fiber faults position can be quickly identified. The fault processing time can be reduced, and the test efficiency and fiber line maintenance quality can be improved.

In the first-level splitting scene, the fiber optic reflector installed on the ONU side. If the reflected return loss of a certain fiber branch is significantly increased compared with the return loss value of the health file, it indicates that there is a problem with the fiber link of this branch. If all the fiber branches with fiber optic reflectors have obvious return loss at the same time, it indicates that the trunk fiber has a fault.

In the second-level splitting scene, the difference of return loss can be compared to accurately locate whether the distribution fiber segment or the indoor fiber segment has attenuation fault. In both the first and second spectral scenes, there will be a steep drop of the reflection peak at the end of the OTDR test curve, so the return loss value of the longest branch link in the ODN may not be accurately measured. It is necessary to measure the variation of the reflector’s reflection level to serve as the basis for fault measurement and diagnosis.

Optical fiber reflectors can also be installed where deployment is required. For example, FBG can be installed before the distribution optical fiber enters the home (FTTH)/ building (FTTB), cooperating with OTDR to determine the fault of indoor/outdoor, in-building/out-building optical fiber. The reflector is considered the best way of implementing real-time end to end(OLT to ONT) monitoring of optical layer in live FTTx networks.

The fiber optic reflector is easy to install in the user’s home, so as to determine the location of the optical path fault through different reflections of the test signal. With wide bandwidth and low insertion loss, the FBG reflectors are ideal components to monitor live network utilizing OTDR at the termination of passive optical network without disturbing traffic. HYC provides FBG fiber optic reflectors of various package types, plastic housing, metal housing, and Pigtail type form SC or LC connector, etc.

HYC Co., Ltd（HYC）is a national Hi-tech optoelectronics company engaged in R&D, manufacture, and marketing of fiber optical products. Providing professional product and service for fiber connectivity, WDM, PLC splitter, and high-density datacom cabling. HYC products and solutions widely applied in 4G/5G, Data Center and Cloud Computing industry, etc.

The selection guide for FBT Splitter and PLC Splitter

The Optical Splitter is one of the most important components connecting the optical line terminal (OLT) and the optical network unit (ONU). Fiber optic splitters enable a signal on an optical fiber to be distributed among two or more fibers. The performance of optical Splitter is directly related to the stability of the entire network link.

The working principle of the optical splitter is: When the light signal is transmitted in a single-mode fiber, the light energy cannot entirely concentrate on the fiber core. A small amount of energy will be spread through the cladding of the fiber. If two fibers are close enough to each other, the transmitting light in an optical fiber can enter into another optical fiber. Therefore, the reallocation technique of optical signal can be achieved in multiple fibers.

From the principle of splitting and the manufacturing process, there are two commonly used types of optical splitters: Fused Biconical Taper(FBT) and Planar Lightwave Circuit (PLC). How to choose between them? What is the difference between in applications?

Fused Biconical Taper (FBT) Splitter
The technology of FBT is that two fibers are placed closely together and fused by applying heat while the assembly is being elongated and tapered. The changes of the splitting ratio will be in real-time monitoring. The taper process will end once the splitting ratio meets the requirements. Keep one fiber (the rest is cut off) as the input port and the other end as the multi-output port.

Planar Lightwave Circuit (PLC) Splitter
PLC splitter is based on planar lightwave circuit technology of quartz glass waveguide. The splitter is composed of an optical splitter chip and an optical fiber array at both ends. The chip is the core component, which has one input and N output. The quality of the chip and the splitter channel directly affect the price of the whole splitter. The optical fiber array is located on the upper surface of the chip and is sealed to form an optical splitter with one input and N output fibers.

How to choose these two devices?
At present, the mature tapering process can only pull 1×4. 1×4 or more devices, with a plurality of 1×2 connected together. For example, 1×8 can be composed of 7 1×2 devices, the whole package in the splitter box. A PLC splitter is available with the splitting ratio of 1:64. The more splitting channels, the more obvious cost advantage. Thus, FBT splitter is more restricted to the number of splits in one coupling. FBT splitters are widely accepted and used in optical networks with few splitting channels requirement. When larger split configurations such as 1×16,1×32,1×48, PLC splitter has more advantages.

What’s more, the material of FBT splitter that is easily available, such as steel, fiber, hot dorm. All of these materials are low-price, making the device itself inexpensive. And the technology of PLC fiber splitter is more complicated and expensive. The device manufacturing process is complex and the technical threshold is high. It uses semiconductor technology for production, greatly increasing the manufacturing difficulty, so its cost is higher.

Since the multichannel FBT splitter is packaged by a plurality of 1×2 connections, which will lead to the large package size and poor uniformity of light splitting. It is impossible for each 1×2 device to be completely evenly divided. While for 1×N splitter, this non-uniformity will be amplified, that will cause a poor uniformity. If good uniformity is required, it needs to be accurately calculated and paired. But it is difficult.

The difference in the distribution of the split ratio is also one of the main differences between them. The splitting ratio of FBT splitter can be real-time monitoring, you can create unequal splitter. It is customizable, and the special types are 1:3, 1:7, 1:11, etc. For PLC splitter, the splitting is uniform, and the signal can be evenly distributed to the user. For example, a 1 x 32 PLC splitter can divide the optical signal equally into 32 shares and then transmit to 32 users. Sometimes, due to the inconsistency of the number of users and the distance, the optical power of different lines needs to be allocated. In this case, devices with different split ratios are needed, and the FBT splitter is used.

Both devices have their own advantages in terms of price and performance. The key to choosing is the occasion and the needs of users in terms of.

HYC Co., Ltd（HYC）is a national Hi-tech optoelectronics company engaged in R&D, manufacture, and marketing of fiber optical products. Providing professional product and service for fiber connectivity, WDM, PLC splitter, and high-density datacom cabling. HYC products and solutions widely applied in 4G/5G, Data Center and Cloud Computing industry, etc.
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