**3. Evaluation of combined FBG optical sensor network and 32-channel spectrum-sliced wavelength-division-multiplexing passive optical network system in simulation environment**

The combined system's simulation setup with the FBG sensor network and SS-WDM PON data channels was developed within RSOFT OptSim software. The simulation setup is shown in **Figure 10**. In this system, only one shared broadband ASE light source is used. ASE spectrum was allocated in the spectral band between from 1533.47 to 1565.50 nm (in frequency band 191.5 THz and 195.5 THz). For SS-WDM PON systems, data transmission channels 1545.7 to 1558.2 nm.

(192.4 THz - 193.95 THz) spectrum was used, whereas 1537.4 to 1545.3 nm (194 THz - 195 THz) spectrum was used for optical FBG sensors network.

ASE light source is connected with an optical power splitter (50%:50%). One of the signal parts is transmitted to AWG MUX for data channel generation, but the second part to OBPF for sensor network. OBPF filtered spectral band from 1537.4 to 1545.3 nm (194 THz - 195 THz) for optical FBG sensor network. 32-channel AWG MUX is used in the setup, that filtered optical signal in the frequency band from 192.4 to 193.95 THz with 50-GHz channel spacing (according to ITU-T G.694.1 recommendation [13]) for 10 Gbit/s NRZ-OOK data channels transmitters. 3-dB bandwidth of each AWG's channel is set to 45 GHz. The data channels bitrate is set to 10 Gbit/s, considering 7% overhead for FEC encoding scheme application resulting in the total bitrate of 10.7 Gbit/s.

Each transmitter block consists of a semiconductor optical amplifier (SOA) to suppress intensity fluctuation noise coming from ASE and electro-absorption modulator (EAM) having immunity to signal polarization state (contrary to MZM). NRZ data signal is generated by data and NRZ component in simulation setup. 32 data channels are coupled with the AWG DEMUX block.

Additionally, DCF is used for dispersion pre-compensation. The transmission line dispersion coefficient is D = 16 ps/nm/km, but the total accumulated dispersion

#### **Figure 10.**

*Simulation setup of combined 32-channel 10 Gbit/s NRZ-OOK modulated SS-WDM-PON system with FBG temperature sensor network.*

**75**

**Figure 11.**

*integrated FBG temperature sensing network.*

**Table 5.**

*Fiber Bragg Grating Sensors Integration in Fiber Optical Systems*

dispersion compensation, 2.7 km long DCF is used.

is 320 ps/nm. DCF fiber dispersion coefficient is −118.5 ps/nm/km, and the attenuation coefficient is α = 0.55 dB/km at 1550 nm reference wavelength. For total

DCF fiber output is connected with one of the OPC input ports, but the second input port is connected with the OBPF output port. The coupled signal is transmitted to OC for separation of the sensor systems signal flows. OC port (2) is connected with 5 optical standard single-mode fiber (ITU-T G.652 recommendation [14]) spans (the length of each span is 4 km, insertion loss is 0.18 dB/km) and 5 FBG temperature sensors network (sensors central wavelength and frequency see in **Table 5**). The spectral band for operation in temperature band −40°C to +80°C (sensor parameters are listed in **Table 3**) is calculated for each sensor. FBG tempera-

The FBG reflected signal from OC port (3) is transmitted to OSA for signal spectrum measurements. Central wavelength or frequency detection, and temperature

AWG MUX filtered signal of 32 channels is transmitted to the receiver block. Each receiver block consists of a variable optical attenuator (VOA), avalanche photodiode (APD), electrical filter (EF), and scope components. In this setup, VOA is used for SS-WDM-PON data channels' BER correlation diagram measurements. InGaAs APD (sensitivity set to −20 dBm at the reference BER of 1012) converts optical signal to digital signal. Electrical Bessel low-pass filter 3-dB bandwidth is set to 6 GHz. The received signal quality is analyzed with the scope component, which

**FBG sensor's No. Central wavelength (nm) Central frequency (THz)**

*BER versus received signal power (BER correlation diagrams) for SS-WDM PON system with and without an* 

 1544.53 194.1 1542.94 194.3 1541.35 194.5 1539.77 194.7 1538.19 194.9 Channel spacing 1.58 0.2

value calculation are realized in a digital signal processor (DSP).

*DOI: http://dx.doi.org/10.5772/intechopen.94289*

ture sensor channel spacing is 200 GHz.

measures signal eye diagrams and BER value.

*FBG temperature sensors central wavelength and frequency.*

*Fiber Bragg Grating Sensors Integration in Fiber Optical Systems DOI: http://dx.doi.org/10.5772/intechopen.94289*

is 320 ps/nm. DCF fiber dispersion coefficient is −118.5 ps/nm/km, and the attenuation coefficient is α = 0.55 dB/km at 1550 nm reference wavelength. For total dispersion compensation, 2.7 km long DCF is used.

DCF fiber output is connected with one of the OPC input ports, but the second input port is connected with the OBPF output port. The coupled signal is transmitted to OC for separation of the sensor systems signal flows. OC port (2) is connected with 5 optical standard single-mode fiber (ITU-T G.652 recommendation [14]) spans (the length of each span is 4 km, insertion loss is 0.18 dB/km) and 5 FBG temperature sensors network (sensors central wavelength and frequency see in **Table 5**). The spectral band for operation in temperature band −40°C to +80°C (sensor parameters are listed in **Table 3**) is calculated for each sensor. FBG temperature sensor channel spacing is 200 GHz.

The FBG reflected signal from OC port (3) is transmitted to OSA for signal spectrum measurements. Central wavelength or frequency detection, and temperature value calculation are realized in a digital signal processor (DSP).

AWG MUX filtered signal of 32 channels is transmitted to the receiver block. Each receiver block consists of a variable optical attenuator (VOA), avalanche photodiode (APD), electrical filter (EF), and scope components. In this setup, VOA is used for SS-WDM-PON data channels' BER correlation diagram measurements. InGaAs APD (sensitivity set to −20 dBm at the reference BER of 1012) converts optical signal to digital signal. Electrical Bessel low-pass filter 3-dB bandwidth is set to 6 GHz. The received signal quality is analyzed with the scope component, which measures signal eye diagrams and BER value.


#### **Table 5.**

*Application of Optical Fiber in Engineering*

ing in the total bitrate of 10.7 Gbit/s.

data channels are coupled with the AWG DEMUX block.

**network system in simulation environment**

compensation fiber (DCF).

can be prevented with chromatic dispersion (CD) compensation, such as dispersion

**3. Evaluation of combined FBG optical sensor network and 32-channel spectrum-sliced wavelength-division-multiplexing passive optical** 

The combined system's simulation setup with the FBG sensor network and SS-WDM PON data channels was developed within RSOFT OptSim software. The simulation setup is shown in **Figure 10**. In this system, only one shared broadband ASE light source is used. ASE spectrum was allocated in the spectral band between from 1533.47 to 1565.50 nm (in frequency band 191.5 THz and 195.5 THz). For SS-WDM PON systems, data transmission channels 1545.7 to 1558.2 nm.

(192.4 THz - 193.95 THz) spectrum was used, whereas 1537.4 to 1545.3 nm (194

ASE light source is connected with an optical power splitter (50%:50%). One of the signal parts is transmitted to AWG MUX for data channel generation, but the second part to OBPF for sensor network. OBPF filtered spectral band from 1537.4 to 1545.3 nm (194 THz - 195 THz) for optical FBG sensor network. 32-channel AWG MUX is used in the setup, that filtered optical signal in the frequency band from 192.4 to 193.95 THz with 50-GHz channel spacing (according to ITU-T G.694.1 recommendation [13]) for 10 Gbit/s NRZ-OOK data channels transmitters. 3-dB bandwidth of each AWG's channel is set to 45 GHz. The data channels bitrate is set to 10 Gbit/s, considering 7% overhead for FEC encoding scheme application result-

Each transmitter block consists of a semiconductor optical amplifier (SOA) to suppress intensity fluctuation noise coming from ASE and electro-absorption modulator (EAM) having immunity to signal polarization state (contrary to MZM). NRZ data signal is generated by data and NRZ component in simulation setup. 32

Additionally, DCF is used for dispersion pre-compensation. The transmission line dispersion coefficient is D = 16 ps/nm/km, but the total accumulated dispersion

*Simulation setup of combined 32-channel 10 Gbit/s NRZ-OOK modulated SS-WDM-PON system with FBG* 

THz - 195 THz) spectrum was used for optical FBG sensors network.

**74**

**Figure 10.**

*temperature sensor network.*

*FBG temperature sensors central wavelength and frequency.*

#### **Figure 11.**

*BER versus received signal power (BER correlation diagrams) for SS-WDM PON system with and without an integrated FBG temperature sensing network.*

The 3rd data channel provided the lowest performance of the combined system (SS-WDM-PON data channels and FBG sensor network). Measured BER versus received signal power, known as BER correlation diagram, for SS-WDM-PON system with and without integrated FBG temperature sensing network is shown in **Figure 11**. BER correlation diagram is measured for the worst-performing (in terms of BER) channel of the SS-WDM PON data transmission system.

As we can see in the measured BER versus received signal power (**Figure 11**) graph, the FBG influence on SS-WDM-PON transmission data channels is minimal. FOTS system power reserve is 19.5 dB at the pre-FEC BER level of 2 × 10−3 [15]. The measured BER value of back-to-back (BTB) systems with SS-WDM PON data channels and FBG sensor network is 3.72 × 10−7, but for back-to-back (BTB) system 1.65 × 10−7.

Based on the measured results, the calculated power penalty value (compared SS-WDM-PON system with and without integrated FBG temperature sensors network) is 0.5 dB at the pre-FEC BER level 2 × 10−3.
