# Experimental Research on In Situ Uniaxial Tensile Response of Silica-Based PLC Optical Splitters
## 2 Experimental Work
### Test Method  
Strength in general stands for resistance to the destructive effects of mechanical factors, such as various loads [24]. The knowledge of adhesive bond strength plays a leading role in the process of their design and operation [25]. In order to simultaneously test the mechanical and optical properties of the PLC optical splitter under uniaxial tensile loading, an online test platform was built in this experiment. The online test platform mainly includes a micro-force universal testing machine (ElectroForce(r) 3200 Series III test instruments from TA Instruments, Eden Prairie, MN, USA) for uniaxial tensile testing and an optical testing instrument for in situ monitoring and recording of the optical properties. The testing campaign of the online test platform for PLC optical splitters are divided in two main topics: (1) mechanical performance, i.e., under uniaxial tensile tests; and (2) optical performance, i.e., the in situ monitoring of the optical performance evolution of the device during uniaxial tensile tests.  
In this work, all the samples were subjected to uniaxial quasi-static tensile tests using a micro-force universal testing machine (ElectroForce(r) 3200 Series III test instruments with a load resolution of 0.1 N) after removing the outer protective shell (stainless steel housing, see Figure 1). In addition, the input and output ports of the sample were looped with an optical power meter in the online test platform to monitor and record the IL of the eight output ports at a wavelength of 1.55 \(\upmu\)m in real-time.  
Control for the ElectroForce(r) 3200 Series III test instruments was provided by the WinTest(r) Digital Control System. Waveform generation, data acquisition, and instrument control were all provided in the comprehensive WinTest package. The ElectroForce linear  
Figure 1: The typical structure of \(1\times 8\) PLC optical splitters: (**a**) side view of a PLC optical splitter module and (**b**) the top view of the PLC (splitter) chip [22].  
motor mover was configured for uniaxial tensile testing system, and its typical control channels include \"Disp\" (displacement), \"Load\", that is, uniaxial tensile testing has displacement control mode and load control mode. A control channel provides a transducer signal as feedback to control the mover in closed-loop control. In displacement control mode, the loading rate is controlled by displacement, and the unit is mm/s; and in load control mode, the loading rate is controlled by force, and the unit is N/s. In order to investigate the effects of different loading control methods and different loading rates on the tensile response of the PLC optical splitter, samples were randomly selected from the same batch of products and divided into three groups according to the loading rate for the uniaxial tensile tests. The tests of the first group were carried in displacement control mode with a loading rate of 0.01 mm/s; the tests of the second and third groups were carried in load control mode with loading rates of 0.1 and 1 N/s, respectively. It should be noted that five samples were selected for each group, and accordingly, a total number of 15 tests were performed to obtain the average failure load at each loading rate. The average failure load was taken as a characterization of the tensile strength of the PLC optical splitter. During the uniaxial tensile test, the load-displacement data and the IL of the eight ports of the specimen were collected for subsequent analysis.