40 and 100 Gb/s Ethernet services have been recently defined and 400G and 1 Tb/s services are anticipated in the future.
Optical transport networks are capable of separating the services provided and the underlying optical transport; service
bandwidths may be larger or smaller than the bandwidth carried on a single optical 'wave'. In this work, we compare
different arrangements of optical transport systems using polarization division multiplexed (PDM) coherent modulation
formats of 4 to 8 bits/symbol for baud rates spanning 8 - 91 GHz. A nonlinear threshold has been defined and nonlinear
performances are compared over 20 uncompensated spans of SMF and NZDSF for various modulation formats. The
finding is that lower baud rate equates to slightly more reach at equal capacity. For example, for 100G using single
carrier vs. dual carrier on a 50 GHz BW, it is observed that for the EDFA-only case, using dual-carrier transmission
yields a reach improvement of 5%, whereas in the Raman-assisted EDFA case, a reach improvement of 4% in favor of
dual-carrier transmission. This shows that one can achieve the same or better optical performance without having to
drive up the baud rate and the speed of associated electro-optics.
In this paper we demonstrate the ability of offset sideband modulation (OSBM) to alleviate problems pertaining to the
electrical crosstalk between upstream and downstream signals in a transceiver used in the optical network unit of a FTTx
system. The OSBM signal consists of an optical carrier and an offset modulated sideband that are created using arbitrary
optical waveform generation. The performance of OSBM is investigated in the context of an inline transceiver, which is
a very simple, next generation, FTTx transceiver. The downstream OSBM bit rate was 2.5 Gbit/s and the upstream OOK
bit rate was 1.25 Gbit/s. A power penalty of only 0.2 dB with respect to an interference free system was observed with
an optical signal to interference ratio (OSIR) as small as -8 dB (the interfering signal power is 8 dB larger than the signal
power). This was the minimum OSIR available with the experimental setup, and it is expected that lower OSIRs can be
A technique is presented for measuring the optical phase transfer function of optoelectronic devices for stimulus frequencies from 100 MHz up to the modulation bandwidth of the device. Using high-resolution optical spectra and a novel instrument setup that makes use of RF signal processing to obtain the stimulus signals, the change in phase of an optical signal is obtained as a function of a time-varying electrical stimulus for electrical-to-optical devices or an optical stimulus for optical-to-optical devices. In the technique, the modulation frequency of the stimulus can be varied over a wide range (e.g., 100 MHz to 10 GHz for a 10 Gb/s device). Thus the proposed technique complements low-frequency and stepped measurements of the optical phase transfer function. The technique is demonstrated by considering the change in phase of the output signal from an electroabsorption modulator as a function of the applied voltage.