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One of the major shortcomings of Centralized Radio Access Networks (C-RAN) is that the large capacity is required for fronthaul network between Remote Radio Heads (RRHs) and central office with baseband unit (BBU) pool. Possible solutions are to introduce lower-cost networking technology for fronthaul network, such as Time and Wavelength Division Multiplexing Passive Optical Network (TWDM-PON), and to introduce functional split, that moves some baseband processing functions to cell site to decrease the utilization of the fronthaul network. In this paper, we construct the mathematical model for selecting function split options of baseband processing to minimize the power consumption of TWDM-PON based fronthaul network. In detail, we formulate the optimization problem for minimizing the total power consumption of fronthaul network in terms of the capacity of TWDM-PON, the number of RRHs in each cell site, server resources, latency constraints, the amount of traffic from each RRH, physical/virtual server power consumption characteristics. Numerical examples are shown for confirming the correctness of the proposed model and for presenting the effect of resource enhancement methods on the capacity and energy efficiency of the system.

This paper presents the world's first field trial of a 40-km reach and over 512-split symmetric-rate 40-Gbit/s λ-tunable time and wavelength division multiplexing passive optical network (TWDM-PON) that utilizes our newly developed high-speed λ-tunable optical network unit transceivers and automatic gain controlled semiconductor optical amplifier-based PON extender for repeater and central office use. The upstream signals for C-band and downstream signals for L+-band in our developed λ-tunable TWDM-PON comply with the wavelength plan of ITU-T G.989 series. In a field trial, we successfully demonstrate error free λ-tunable transmission for the 40-km reach and 1024-split (maximum number) symmetric-rate 40-Gbit/s λ-tunable TWDM-PON over installed standard single-mode fiber links, and advanced network functions such as dynamic load balancing, incremental system upgrade, optical subscriber unit protection, and OLT equipment power saving are also confirmed.

World-first coexistence trial of TDM and CDM giga-bit passive optical networks (PONs) was successfully completed. A very shallow minimum isolation of 7 dB between G- and CDM-PON at OLT and ONU in the ITU-T G.984.5 enhancement band was demonstrated. The feasibility of bidirectional transmission on the same wavelength was confirmed. The backscattering optical noise does not seriously affect the maximum reach of CDM-PON. Adding the CDM-PON onto GPON can provide following technical and economical impacts: low-cost coexistence, minimum service outage, and combination of best-effort and guaranteed-bandwidth for efficient and high-quality network services due to CDM feature.

In this paper, next-generation ultralong reach code division multiplexing (CDM) on fiber (COF) passive optical network (COF-PON) based on CDM (multiplexing carried out in electrical domain) presented here. We describe the system configuration, COF transceiver, key merits such as bidirectional transmission (on the same wavelength with single fiber), extending the reach by coding gain, and offering huge bandwidth to large number of subscribers by overlaying on coarse wavelength division multiplexing (CWDM)/wavelength division multiplexing (WDM). We believe our newly proposed ultralong reach COF-PON will help to drastically reduce the Capex and Opex costs by consolidating metro and access networks into one simple network. We demonstrated initial experimental results over 100-km bidirectional COF-PON overlay on 4lambda-CWDM channels' transmission without the use of an optical amplifier

In this letter, we demonstrate the decoding stability of an optical hybrid filter (OHF) node module for an adaptive network to an environment temperature fluctuation. [Error free] signal decoding was observed from a temperature range of 0° to 60°. Improving athermal mounting technology would expand the applicable temperature range of an OHF node module as the passive node.

We introduce the world's first field trial of a symmetric-rate 40-Gbit/s λ-tunable WDM/TDM-PON that uses a high-speed λ-selective ONU TRx and optical extender. 40-km reach and 1024-split λ-switching transmission, and system demonstrations are successfully performed.

We proposed a wavelength swept discovery process for λ-tunable WDM/TDM-PON system. Our discovery process is successfully demonstrated on the λ-tunable WDM/TDM-PON prototype. We also confirmed that the ONU can receive the discovery message at any wavelength.

We clarified the relationship between the extinction ratio of upstream burst signals and Q factor of received signals to evaluate the impact of beat noise caused by residual noise interferences.

Virtualized PON is a next generation optical access system which reduces power consumption by sleeping OLTs according to traffic volume. Simulation results show the number of activated OLTs has a relationship with TCP control mechanisms.

First demonstration of the bandwidth allocation method for Virtualized PON was presented. To validate the principle of this method, we carried out field trial of 10Gbps-90km transmission using 10G-EPON system. We accomplished control of the user bandwidth.

First time, we have experimentally demonstrated 1.25-Gbps/subscriber 10-Gchip/s ECDM-PON upstream transmission over 20-km SSMF using WDM light sources. Additionally, optical beating induced performance degradation was investigated by varying WDM channel spacing from 100-GHz to 10-GHz.

First time 8-channels electrically code division multiplexing technique for optical access networks is demonstrated at a chip-rate of 10 Gchip/s. The technique enables error-free transmission of 1.25 Gbit/s × 8-channels over 20 km single-mode-fiber.

Code-division-multiplexing (CDM) -Technologies for next-generation passive optical networks (PON) is discussed. The PON using CDM are reviewed in the view point of alternative for next generation PON. Architecture of electrical CDM-PON is discussed, and its attractive feature is introduced. Co-existing electrical CDM-PON and G-PON as a potential candidate of next generation optical access network was demonstrated.

This paper describes a novel DBA (Dynamic Bandwidth Allocation) mechanism and evaluation results obtained by simulations and FPGA implementation experiments for CDMA-PONs. It improves non-blocking probability about 10% to 50% compared with a conventional method.

First time hybrid OTDM and OCDM technology is presented here to realize asymmetric 160Gbps PON System. To validate the basic principle, we experimentally demonstrated 2 channels OCDM signals with 15chip (∼1.6ps/chip) pseudo random type optical encoder by allocating encoded chip pulses of different channels with 0.1ps accuracy.

Coexistence trial of TDM and CDM giga-bit passive optical networks (PONs) was successfully completed. A very shallow minimum isolation of 7 dB between G- and CDM-PON at OLT and ONU in the ITU-T G.984.5 enhancement band was demonstrated. The backscattering optical noise does not seriously affect the maximum reach of CDM-PON. Adding the CDM-PON onto GPON can provide following technical and economical impacts: low-cost coexistence, minimum service outage, and combination of best-effort and guaranteed-bandwidth for efficient and high-quality network services due to CDM feature.

First demonstration of asymmetric PON system (10 Gbps × 16 ch downstream) using OTDM and OCDM technologies is presented. We accomplished a transmission over 20 km SMF with optimized dispersion tolerance.

Next generation long reach hybrid WDM-CDM-PON based on Code Division Multiplexing presented here. We describe system configuration, key merits such as bidirectional transmission (on same wavelength), extend the reach by coding gain and simplified network solution. We show initial experimental results over 100km bidirectional, multi-channels CWDM transmission without an optical amplifier.

Here we presented a noble passive optical network based on Code Division Multiplexing (CDM) on fiber "COF" and demonstrated over 100km bidirectional 4-channels CWDM transmission without optical amplifier. We outline COF-PON architecture, key merits it offer, such as coding gain to improve the receiver sensitivity, bidirectional transmission (on same wavelength), colorless operation and experimental results. We believe our newly propose ultra long reach COF-PON will help drastically reduce the CapEx and OpEx cost by consolidating metro and access networks into simple one network.

First time, an unprecedented 42 dB loss budget was realized by using hybrid DWDM-CDM (code division multiplexing)-PON without optical amplifier. We experimentally demonstrated 100 km 16lambda-DWDM-CDM-PON bidirectional transmission with 62.5 Mbps times 32 users/lambda symmetry guaranteed bandwidth. Long reach PON is expected to reduce CapEx and OpEx cost.