This paper proposes a novel power-saving mechanism for the 10 Gbit/s Ethernet passive optical network (10G-EPON) systems that are currently being discussed in IEEE 802.3av. The proposed power-saving mechanism includes a sleep control function and an adaptive link rate (ALR) control function. The sleep control function switches the modes of optical network units (ONUs), i.e. active and sleep modes, depending on the presence or absence of traffic. The ALR control function switches the link rate between the optical line terminal (OLT) and an ONU, i.e. 1 Gbit/s or 10 Gbit/s, depending on the quantity of traffic. The proposed hybrid mechanism offers effective power management of ONUs on the basis of the traffic conditions. The proposed hybrid mechanism is validated by some numerical simulations.

This paper proposes an optical access system that enables voice communication services to continue when a power failure occurs. In particular, we propose applying a digital signal processing technique namely blind speech separation (BSS) to an optical multiple access system for demultiplexing randomly mixture signals received from an upstream user. We present a brief overview and the target of proposed system and describe the key technique, namely the BSS procedure. We then report system feasibility studies for the first step of a numerical simulation (assuming two wavelengths and three users) and experimental tests (assuming two wavelengths and two users) using actual sample voice signals. We confirmed that separation was realized by using a subjective assessment that consisted of listening to obtained signals.

Deployment strategy of access systems is described toward next generation access (NGA). Considering service requirements and consecutive evolution to NGA, we think that 10 Gbit TDM-PON will be the most promising system among several technologies. The other systems like WDM-PON, for which we have not yet found a suitable segment of users, can contribute to high-end access services with scalability and reliability.

A novel super wideband optical FM modulation scheme that employs an optical heterodyne detection technique is proposed and demonstrated. The experimental results show that applying this scheme to 40-channel AM video transmission expands the power budget by approximately 10 dB at a carrier- to-noise ratio (CNR) of 42 dB. The feasibility of the scheme is also discussed from the viewpoints of connector reflectivity and fiber-dispersion.

The author describes an error correction system for digital subscriber loop transmission systems which use time compression multiplexing (TCM). An interleaved block code is used to correct the burst errors due to impulse noise from analog telephone circuits. This interleaving method requires no extra hardware and contributes no additional delay. To evaluate the transmission performance of this error correction system, the bit error rate after decoding is derived on the basis of a burst error model for 200 kb/s digital subscriber transmission using the alternate mark inversion (AMI) line code. The experimental results for a 200 kb/s TCM system show that burst errors are substantially reduced.>