Centralized Monitoring for Huge FTTH Network using Code Grating

The Covid-19 has impacted the demand in broadband communication specifically in Fiber to the Home (FTTH). The increase in the demand caused the increase in the number of users in Triple play service during the Movement Control Order (MCO) period. Consequently, the high volume of user has slowed down the internet speed and connectivity. In addition, there is no effective monitoring system to monitor the network health from user end. This study was conducted to design a PON Fiber-to-the-Home (FTTH) network which can serve thousands of users by increasing the capacity of the network and at the same time the network operator will be able to monitor any faulty branch(s) at the user end. By upgrading the new component in PON FTTH such as SOA, AWG and Demultiplexer, the network is able to support up to 30 000 users and also able to monitor fault user branches in FTTH network by using code FBG.


1.
Introduction When Covid-19 pandemic strike Malaysia in 2020, the network operator experience very high demand in broadband communication service and it been reported that 50% to 70% increase of internet traffic data connected in the residential areas [1].With drastically increase the number of users in Triple play service during the Movement Control Order (MCO) period has slowed down the internet speed [2].Due to this, total of 32, 485 complaints received on poor or no 4G connection coverage in July to October 2021 period [3].
Passive optical network (PON) based FTTH access network is the best structure which can provide a higher bandwidth to the users [4,5].Fiber Bragg Grating (FBG) is low-cost filter which will attached with optical fiber.FBG operation using principle of diffraction grating where when the light travels inside the grating structure some light will reflect back as Bragg wavelength.The wavelength of FBG (Bragg wavelength) is given by equation (1).
= 2   (1) Where  is the grating period,   is the effective core refractive index and   is the Bragg wavelength.When Bragg condition is met, all the reflected light constructively adds up to form backward reflected peak whose central wavelength is given by   [6].FBG as detection and identify failure branches is the most cost-effective monitoring solution and suitable for P2MP access network [7].The FBG been coded using binary code to represent each ONU [8].Any faulty ONU can be observed in OSA and analysis by using the code.This method able to monitor up to 256 ONU with different FBG binary code.However, this method needs to used more than one FBG in one branch to represent each ONU.Total up to 512 FBG needed to monitor 256 ONU.A Uniform and Phase-Shifted Fiber Bragg Grating used to monitor the faulty branches [9].This method used low cost super luminescent diode (SLED) as the monitoring signal.This method able to detect and identified the fault location, however the use of SLED is difficult because the input power is low and it may affect the receiver if the transmitter and receiver is far and can only monitor several users.
The purpose of the study is to design and propose an effective monitoring system for PON H-FTTH network by using coded FBG to address the challenges faced by network operators.

2.
Design Consideration In this paper, a centralized monitoring system with low power monitoring signal and broad bandwidth (Huge Fiber to the Home) for WDM PON is proposed as per shown in Figure 1.The PON FTTH network has been modified by using Optisystem 12 software simulation.At each ONU will be place one FBG as monitoring system.The reflected wavelength from the FBG is coded by the position of each ONU.The reflected spectrum will be analyzed using OSA.This reflected wavelength will be analysis.If there is no reflected wavelength, its show that there is a faulty ONU and the data was not been transmitted to user.
For DP the FBG will be coded by 1601.0 nm, 1602.0 nm, 1603.0 nm indicate DP 1 until DP 3 respectively.For ONU, each DP will have 8 ONU for example, the number of ONU 1 until ONU 8 will be coded as 1601.1 nm, 1601.2 nm, 1601.3 nm respectively as show in Figure 4.The reflectivity and bandwidth also will be varying depend on the DP and ONU numbers for display purposed in OSA.DP's reflectivity is 0.9 and bandwidth 0.01nm while for ONU the reflectivity is 0.8 and bandwidth 0.02nm as shown in Figure 2. The higher the reflectivity number the better the of reflected signal been reflect at core network.And for bandwidth, the larger number of bandwidths will cause the reflected signal been overlap and it is difficult for the operator to distinguish which ONU is broken.The analysis the BER and Q-factor performance the splitting ratio of WDM Demux has been varied to make sure the network can support maximum number of users.With 4 splitting ratio, 10 240 users can use the network with Q-factor 10.2125 and BER performance is 5.58494e-025.While for 32 splitting ratios, Q-factor 9.75384 and BER performance is 5.81494e-023 which can support 81 900 users.From the result, it shows that the higher the splitting ratio, the higher the number of users can support by the system but the lower the Q-factor.

Conclusion
A monitoring system for huge FTTH system is successfully presented.In conclusion, the higher the number of users, the lower Q-factor and the smaller the BER value.In increasing the number of users, the monitoring fault(s) branch able to detect by using reflected signal of coded FBG.

Figure 1 .
Figure 1.Block diagram for Huge FTTH with monitoring system.

Figure 3
Figure3show all reflected wavelength from OSA.To verify the system capable to detect faulty branch, attenuator will be placed and act as noise.As show in Figure4, failure in ONU 3 from DP 1.With this the failure ONU or DP are easily monitor and give advantage to the network operator to do maintenance.