Low-cost ultrahigh areal density optical disc system towards 400 Gbyte/disc

We introduce a new 400 Gbyte disc system, which has twice as much areal density as BDXL™ does, retaining the use of the conventional optical head and disc technology. Our proposal is based on the application of code modulations with enlarged minimum run length (d) and land/groove (L/G) geometry to increase linear recording density and track density by 1.5 and 1.33 times, respectively. Also, saw tooth wobble (STW) was introduced for a multilayered L/G disc system to suppress readout signal fluctuations. Here, we demonstrated that the linear recording density increased to 45.5 Gbyte/layer by applying d = 3 to a commercially available BDXL™. Also, we checked that crosstalk, which is a major concern in an L/G disc with a track pitch of 240 nm, was suppressed to below −30 dB by choosing the proper groove depth. Moreover, the investigation of the effect of track width modulation on the write/read performance demonstrated that an adverse influence can be suppressed by employing STW.