State-of-the-art and perspectives for long-wavelength high speed VCSELs

Abstract

In this work, the latest advances in 1550 nm high-speed short-cavity (SC) VCSELs are presented. The electrical, optical and thermal design of these devices is discussed with respect to their high-speed modulation behaviour. The implemented design improvements allow high output powers for ambient temperatures up to 90 °C, high differential quantum efficiencies up to 45%, low thermal resistances down to 1.6 K/mW, small-signal modulation bandwidths in excess of 17 GHz, and error-free data transmission at room-temperature at data rates of 25 Gbit/s over 4.2 km of single-mode fiber and 35 Gbit/s in back to back (B2B) configuration. The latter corresponds to rather small energies per bit of only 0.23 pJ/bit. At elevated temperatures of 55°C error-free transmission is achieved at 25 Gbit/s in B2B configuration.

Low power consumption O-band VCSEL sources for upstream channels in PON systems

“…These two factors explain the higher power penalty for this signal, which is still below 1.5dB. New developments in the area of VCSEL fabrication indicate that modulation frequencies in excess of 20-30 GHz are feasible in prototypes [5] and hence improvements in the current results possible.…”

Challenges in Polybinary Modulation for Bandwidth Limited Optical Links

“…Table 1 The challenge in generating the optical polybinary signal, beyond the filter adequacy, arises in the need of large extinction ratios. In short-range systems, vertical-cavity surface-emitting lasers (VCSELs) are the most common building block due to their manufacturability; however, VCSELs have two main drawbacks in terms of performance: reduced bandwidth compared to other directly modulated type of laser sources and limited extinction ratio [11]. State-of-the-art VCSELs have been demonstrated to work in multi-GHz regimes, providing a platform to operate in >25 Gbit/s rates [12,13], and therefore, bandwidth limitations are being overcome.…”

“…The simplest method to generate a polybinary signal is filtering the high frequency components of the original electrical signal with a Bessel low-pass filter (LPF) [11]. A Bessel filter is a filter derived using Bessel functions with a goal of linear phase, i.e., maximally flat group delay, which implies a time delay constant for any frequency component [16].…”