Optical disc writing strategy for analog signal recording
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SPECIAL SECTION: REGULAR PAPER International Symposium on Imaging, Sensing, and Optical Memory (ISOM’ 19), Niigata, Japan
Optical disc writing strategy for analog signal recording Kimihiro Saito1 Received: 26 January 2020 / Accepted: 30 July 2020 © The Optical Society of Japan 2020
Abstract Optical discs are being sought as low-cost, earth-friendly storage candidates in response to increasing data volumes. To increase the recording density of optical disc, analog recording technique such as the Orthogonal Frequency Division Multiplexing (OFDM) method has been investigated. Since bitwise information is recorded on optical discs, it is necessary to create a column of marks corresponding to the analog signal for the OFDM method. The Delta-Sigma Modulation (DSM) is known as an analog to digital conversion method in the area of audio. This method transfers efficiently an analog signal to a binary sequence with a simple circuit. In this paper, the application of the method for analog signal recording and the simulation results of the mark recording process on the optical disc are described. The optical disc recording utilizes temperature rise of a multilayer film stack in recording process that is triggered by light focusing. A simplified, 2.5-dimension, thermal analysis is applied to do the large-scale simulation of recording mark sequence.
1 Introduction As the huge amount of data increase, earth friendly and lowcost storage system is required [1]. Optical disc systems are candidate to achieve such data storage systems. Optical discs such as BD™, BDXL™ [2, 3] and AD [4] discs are currently demonstrated in the market. These discs use phase change materials and employ the partial response maximum likelihood (PRML) [4–9] method for signal processing. The class IV partial response signaling for data detection was first applied to magnetic recording [10–14]. To further increase the recording density of optical disc, analog recording technique such as the Orthogonal Frequency Division Multiplexing (OFDM) [15–19] method has been investigated. In the application of the OFDM, the data sequence is separated in a set of frequency sub-bands and then recorded on the disc. Defocus and disc tilt cause deformation of optical transfer function. Since the deformation changes only the amplitudes of the information sub-bands, they can easily be recovered.
* Kimihiro Saito [email protected] 1
The information data is recorded bitwise as a mark sequence on optical disc systems. Therefore, the analog signal generated by the OFDM method should be converted to a binary signal. I tried to use the Delta-Sigma Modulation (DSM) [20, 21] that is known as an analog to digital conversion method in the area of audio. This method transfers efficiently an analog signal to a binary sequence with a simple circuit. The recording marks and readout signal using the OFDM and the DSM method are computer simulated with an optical pickup and recording medium. A sequence of large number of marks is necessary to evaluate a signal quality for the calculation
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