(a) Measured performance of the 220/230 GHz FSF. The red and blue lines show the transmission efficiencies from the input port to the LSB and USB output ports, respectively. The dots show the measurement results, and the dashed lines show the simulated performance, as in figure 6b. (b) Results of additional simulation of the 220/230 GHz FSF with different dimensions to consider the machining error. The black dots show the measurement results, and the red and blue lines show the LSB and USB outputs of the additional simulation, respectively, which accurately reproduced the measured performance. (Color online)