In this Letter we report on an all-optical-fiber approach to the generation of ultra-low-noise microwave signals. We make use of two erbium fiber mode-locked lasers phase locked to a common ultrastable laser source to generate an $11.55\mathrm{GHz}$ signal with an unprecedented relative phase noise of $-111\mathrm{dBc}∕\mathrm{Hz}$ at $1\mathrm{Hz}$ from the carrier. The residual frequency instability of the microwave signals derived from the two optical frequency combs is below $2.3\times {10}^{-16}$ at $1\mathrm{s}$ and about $4\times {10}^{-19}$ at $6.5\times {10}^4\mathrm{s}$ (in $5\mathrm{Hz}$ bandwidth, three days of continuous operation).