Abstract
We demonstrate up to 100 Gbaud quadrature-amplitude modulated (QAM) signal generation with monolithic silicon in-phase quadrature (I/Q)-modulator based on silicon-germanium (SiGe) electro-absorption modulators (EAM). The modulator is in a differentially driven Mach–Zehnder (MZ) interferometric configuration similar to the conventional MZ modulator (MZM) based (I/Q) modulators. In particular, single-polarization quadrature phase-shift keying (SP-QPSK) signaling at symbol rates of 100 Gbaud with BERs below the hard-decision forward error correction (FEC) limit is shown. SP-QPSK optical signal generation and transmission over 80 km single-mode fiber (SMF) are demonstrated at symbol rates of 50 Gbaud with BER of less than $\mathbf {10^{-5}}$ . The effect of the frequency roll-off used for Nyquist pulse shaping with raised cosine frequency response is studied for SP-QPSK 50 Gbaud signals. Furthermore, 16QAM signals at symbol rates of 50 Gbaud are generated.
Highlights
Q UADRATURE-AMPLITUDE modulated (QAM) optical signals are usually generated in a nested Mach-Zehnder interferometer (MZI) comprising several stages of optical power splitters and high-speed modulators which allow for either phase or amplitude modulation
Quadrature-phase shift keying (QPSK) signaling at symbol rates of 32.5 Gbaud with a 4-arm indium phosphide (InP) electro-absorption modulators (EAM) based In-phase and quadrature (I/Q) modulator is reported in [20]
We demonstrate to the best of our knowledge the highest symbol rates for QPSK and 16QAM signals so far generated from EAM based I/Q modulators
Summary
Q UADRATURE-AMPLITUDE modulated (QAM) optical signals are usually generated in a nested Mach-Zehnder interferometer (MZI) comprising several stages of optical power splitters and high-speed modulators which allow for either phase or amplitude modulation. QPSK signaling at symbol rates of 32.5 Gbaud with a 4-arm InP EAM based I/Q modulator is reported in [20]. SiGe EAM based 3-arm I/Q modulator is demonstrated for 16QAM signaling at the symbol rates 20 Gbaud [21], only. QAM signal generation at relevant symbol rates using these compact, high-speed and energy-efficient EAM devices still need to be demonstrated. Single-polarization QPSK generation at symbol rates of 100 Gbaud is demonstrated, which is – to the best of our knowledge – a record signaling speed for EAM based I/Q modulators. Of the MZIs are defined by the direct current (DC) phase shifters based on the thermo-optic effect in silicon
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