Browsing by Subject "bleaching"
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Item Impact of Nonlinearity in an MUTC Photodetector on an RF-Modulated Frequency Comb(IEEE, 2019-11-21) Mahabadi, Seyed Ehsan Jamali; Carruthers, Thomas F.; Menyuk, Curtis; Hutchinson, Meredith N.; McKinney, Jason D.; Williams, Keith J.Abstract—We calculate the impact of nonlinearity in an MUTC photodetector on an RF-modulated frequency comb, taking into account bleaching (gain saturation). An RF-modulated frequency comb is characterized by a distinct IMD2ₙ and IMD3ₙ and hence a distinct OIP2ₙ and OIP3ₙ for each comb line nItem Impact of Nonlinearity on RF-Modulated Frequency Combs with Different Modulation Depths in an MUTC Photodetector(IEEE, 2019-11-07) Mahabadi, Seyed Ehsan Jamali; Carruthers, Thomas F.; Menyuk, Curtis; Hutchinson, Meredith N.; McKinney, Jason D.; Williams, Keith J.We calculate the impact of nonlinearity in a modified uni-traveling carrier (MUTC) photodetector on an RF-modulated frequency comb that is generated using short optical pulses. We take into account bleaching (nonlinear saturation), which plays an important role due to the large peak-to-average power ratio. Nonlinear impairment of an RF-modulated continuous wave is characterized by the second- and third-order intermodulation distortion (IMD2 and IMD3). By contrast, an RF-modulated frequency comb is characterized by a distinct IMD2ₙ and IMD3ₙ for each comb line n. We study the effect of modulation depth on nonlinearity in frequency combs, comparing modulation depths of 4% and 8%. When we include bleaching, we find that the OIP3ₙ, third-order intercept point for the n-th comb line, increases when the modulation depth increases for comb lines at frequencies above 2 GHz (n >= 40), so that distortion decreases. We show that this effect occurs because bleaching attenuates lower frequencies more than higher frequencies and this preferential attenuation increases as the modulation depth increases.