Design constraints of photonic-lantern spatial multiplexer based on laser-inscribed 3-D waveguide technology

Laser-inscribed 3-D waveguide (3DW) technology has been applied to realize photonic-lantern spatial multiplexer (SMUX), which potentially enables lossless mode (de)multiplexing. However, the index contrast Δn between the transparent substrate and the spatially-inscribed waveguides by femto-second laser pulses is generally smaller than 6 × 10-3. It is simulated that a 3DW SMUX with Δ n <6 × 10-3 is able to provide a low mode-dependent loss (MDL) and coupler insertion loss (CIL) when coupling to a three-mode few-mode fiber (FMF). However, in six-and 15-mode cases, to guide all supermodes, few-mode region created by coupled or merged waveguides at the FMF side of the 3DW SMUX cannot be very small. This results in mode-profile mismatch between the 3DW SMUX and a low differential-group-delay FMF, which is generally with Δn around 1 × 10-2. Instead of employing bulky imaging optics, uptapering FMF is proposed to enlarge the modes of the FMF for minimizing the mode-profile mismatch. Simulation shows MDL and CIL enhancement can be achieved by the uptapering solution. It also points out that as mode number increases to 15, although uptapering FMF still improves coupling performance, low MDL <1dB cannot be acquired with Δ n <= 6 × 10-3. In order to achieve a lossless mode (de)multiplexing for 15 spatial modes, Δ n = 1 × 10-2 is required for a 15-core 3DW SMUX. Moreover, a fully-packaged dual-channel 3DW coupling circuit including two six-mode SMUXes is introduced and experimentally demonstrated. MDL = 7 and CIL <8 dB is achieved in a loop through measurement with the two SMUXes. Mode-profile mismatch due to the limited Δn of the 3DW device is solved by uptapering FMF with a factor of 1.4

POF application in home systems and local systems

The large bandwidth and ease of installation make POF a very attractive medium for low-cost broadband in-building networks, in which several independent sets of services are integrated. Adaptive subcarrier multiplexing can combine services with widely differing characteristics in a single POF network, among which high-capacity wireless LANs by deploying the Optical Frequency Multiplying radio-over-fibre technology

Recent research results on flexible optical access and in-building networks

Optical fibre networks are bringing a range of high capacity services to the user’s home. By applying optical fibre inside his home as well, this potential can be extended readily up to the user himself. Optical routing techniques provide additional flexibility in the access and in-building network, and thus improve the efficiency with which the network’s resources are used. Recent research achievements in the COBRA institute are reported on flexible optical routing techniques for delivery of wired and wireless services

Long-haul transmission of PM-16QAM, PM-32QAM and PM-64QAM based terabit superchannels over a field deployed legacy fiber

Increase in transmission symbol-rate as well as order of quadrature amplitude modulation (QAM) is identified as the most economical way to reduce cost per transmitted bit. In particular, next generation transponders aim at supporting datarates up to 1 Tb/s employing superchannels due to electrical components’ bandwidth limitations. Furthermore, the introduction of a flexible-grid architecture can maximize throughput by minimizing spectral gaps in available optical spectrum. Keeping in view these design options, we conducted several high capacity experiments with tier1 operator Orange using their field deployed standard single mode fiber (SSMF, G.652), having a total length of 762 km, connecting the cities Lyon and Marseille in France. In particular we employed four subcarriers per Tb/s superchannel, each modulated by PM-16QAM, PM-32QAM and PM-64QAM with per carrier symbol-rates of 41.2 GBd, 33 GBd and 34 GBd, respectively. The subcarrier spacing was 50 GHz for the PM- 16QAM case and 37.5 GHz for both the PM-32QAM and PM-64QAM cases allowing in total 241.0 Tb/s, 321.0 Tb/s and 321.2 Tb/s superchannels over C-band and resulting in potential C-band capacities of 24.0 Tb/s, 32.0 Tb/s and 38.4 Tb/s, respectively. After field transmission the maximum available OSNR0:1nm margin compared to the required OSNR0:1nm at forward error correction (FEC) threshold was 8.2 dB, 5.4 dB and 4.2 dB for PM-16QAM, PM-32QAM and PM-64QAM, respectively. The transmission reach for PM-16QAM and PM- 32QAM modulated superchannels was extended to 1571 km and 1065 km using erbium doped fiber amplified SSMF spans of 101 km length

Multi-flex field trial over 762km of G. 652 SSMF using programmable modulation formats up to 64QAM

We demonstrate next-generation network upgrade scenarios using flexi-format (PM-QPSK→PM-64QAM) and flexi-rate (100G→300G) transmission over field-deployed fiber (762km). The back-to-back penalties are limited to ~2.6dB, whereas after transmission, available margin in excess of ~7.6dB is reported