Fig. 1. Schematic diagram of small-signal frequency response measurement for PDs

Fig. 2. Schematic diagram of large-signal frequency response (IMD3) measurement for PDs

Fig. 3. Measured electrical power at different frequencies in photocurrent generated by PD. (a) 1-fold frequency i_L(f₁;m₁,m_b); (b) 2-fold frequency i_L(2f₁+f_b;m₁,m_b); (c) 3-fold frequency i_L(3f₁;m₁,m_b); (d) 4-fold frequency i_L(4f₁+f_b;m₁,m_b)

Fig. 4. Measured amplitude ratio i_L(f_b;m₁,m_b)/i_L(f_b;0,m_b) of the pilot-tone signal and modulation coefficient m₁(f₁) of MZM1. (a) 1-fold frequency; (b) 2-fold frequency; (c) 3-fold frequency; (d) 4-fold frequency

Fig. 5. Calculated modulation response of MZM1. (a) 1-fold frequency J₁[m₁(f₁)]; (b) 2-fold frequency J₂[m₁(f₁)]; (c) 3-fold frequency J₃[m₁(f₁)]; (d) 4-fold frequency J₄[m₁(f₁)]

Fig. 6. Comparison of measured small-signal frequency response of PD with our method and two-tone modulation method. (a) 1-fold frequency; (b) 2-fold frequency; (c) 3-fold frequency; (d) 4-fold frequency

Fig. 7. Measured reflection coefficient of the PD under test on a Smith chart

Fig. 8. Measured electrical power of nonlinear photocurrent signals generated by PD when MZMs input power P₁(P₂) is 7, 9, 11, and 13 dBm, respectively. (a) Fundamental frequency f₁; (b) i_NL1(2f₁-f₂)

Fig. 9. Measured modulation coefficient m₁ of MZM1 and modulation spurious response J₂(2m₁)/2J₁²(m₁) when MZM1 input power P₁ is 7, 9, 11, and 13 dBm, respectively

Fig. 10. Extracted electrical power i_NL2(2f₁-f₂) of the IMD3 of PD when MZMs input power P₁(P₂) is 7, 9, 11, and 13 dBm, respectively

Fig. 11. Three-dimensional fitting surfaces of fundamental frequency f₁, measurable nonlinear photocurrent i_NL1(2f₁-f₂), and IMD3 i_NL2(2f₁-f₂)

Fig. 12. Comparison of measured frequency-dependent OIP3 of PD with our method and four-carrier beating method, and the inset shows the case near 5 GHz