Derek Nesset

NG-PON2 Technology and Standards

This paper provides a tutorial overview of the latest generation of passive optical network (PON) technology standards nearing completion in ITU-T. The system is termed NG-PON2 and offers a fiber capacity of 40 Gbit/s by exploiting multiple wavelengths at dense wavelength division multiplexing channel spacing and tunable transceiver technology in the subscriber terminals (ONUs). Here, the focus is on the requirements from network operators that are driving the standards developments and the technology selection prior to standardization. A prestandard view of the main physical layer optical specifications is also given, ahead of final ITU-T approval.

A 135-km 8192-Split Carrier Distributed DWDM-TDMA PON With 2

We present a hybrid dense wavelength-division-multiplexed time-division multiple access passive optical network (DWDM-TDMA PON) with record performance in terms of reach (135.1 km of which 124 km were field-installed fibers), number of supported optical network units (ONUs-8192) and capacity (symmetric 320 Gb/s). This was done using 32-, 50-GHz-spaced downstream wavelengths and another 32-, 50-GHz-spaced upstream wavelengths, each carrying 10 Gb/s traffic (256 ONUs per wavelength, upstream operated in burst mode). The 10 Gb/s downstream channels were based upon DFB lasers (arranged in a DWDM grid), whose outputs were modulated using a electro-absorption modulator (EAM). The downstream channels were terminated using avalanche photodiodes in the optical networks units (ONUs). Erbium-doped fiber amplifiers (EDFAs) provided the gain to overcome the large fiber and splitting losses. The 10 Gb/s upstream channels were based upon seed carriers (arranged in a DWDM grid) distributed from the service node towards the optical network units (ONUs) located in the users premises. The ONUs boosted, modulated, and reflected these seed carriers back toward the service node using integrated 10 Gb/s reflective EAM-SOAs (EAM-semiconductor optical amplifier). This seed carrier distribution scheme offers the advantage that all wavelength referencing is done in the well-controlled environment of the service node. The bursty upstream channels were further supported by gain stabilized EDFAs and a 3R 10 Gb/s burst-mode receiver with electronic dispersion compensation. The demonstrated network concept allows integration of metro and optical access networks into a single all-optical system, which has potential for capital and operational expenditure savings for operators.

\,\times\,

Feature Issue on Passive Optical Network Architectures and TechnologiesWe describe how a passive optical network (PON) extender box can be implemented at standard PON wavelengths (1310 and 1490nm) using either optical fiber amplifiers (praseodymium and thulium) or semiconductor optical amplifiers to further increase the physical reach and split of a current standardized PON system such as a G-PON or GE-PON. The transparency to PON protocol of this approach means no changes to the existing standards are required. This is attractive as operators and vendors are keen to fully exploit the investment made in current PON standards.

32

We report on a hybrid DWDM-TDM A optical access network that provides a route for integrating access and metro net- works into a single all-optical system. The greatest challenge in using DWDM in optical access networks is to precisely align the wavelength of the customer transmitter (Tx) with a DWDM wave- length grid at low cost. Here, this was achieved using novel tunable, external cavity lasers in the optical network units (ONUs) at the customers end. To further support the upstream link, a 10 Gb/s burst mode receiver (BMRx) was developed and gain-stabilized erbium-doped fiber amplifiers (EDFAs) were used in the network experiments. The experimental results show that 10 Gb/s bit rates can be achieved both in the downstream and upstream (operated in burst mode) direction over a reach of 100 km. Up to 32 × 50 GHz spaced downstream wavelengths and another 32 × 50 GHz spaced upstream wavelengths can be supported. A 512 split per wave- length was achieved: the network is then capable of distributing a symmetric 320 Gb/s capacity to 16384 customers. The proposed architecture is a potential candidate for future optical access net- works. Indeed it spreads the cost of the network equipment over a very large customer base, allows for node consolidation and integration of metro and optical access networks into an all-optical system.

\,\times\,

A DWDM-TDMA PON using carrier distribution with symmetric 320 Gb/s capacity is demonstrated over 124 km field-installed fibers. The upstream channels feature a 3R 10 Gb/s burst-mode receiver with electronic dispersion compensation, burst-mode EDFAs and integrated reflective SOA-EAMs.

10 Gb/s Capacity

This is the second of a two-part paper intended to provide technical insight and rationales behind the recently approved ITU-T G.989.2 Recommendation: the physical media dependent layer specification of the 40-gigabit-capable passive optical networks (NG-PON2). While Part 1 of the paper discusses topics related to the optical link design, Part 2 focuses on wavelength control, technology feasibility, management and control channel design, and potential future standardization directions of such a multi-wavelength PON system. As the NG-PON2 system will continue to evolve, technology extensions are also discussed to provide guidance for future research.

Amplified gigabit PON systems [Invited]

NG-PON2 is the industrys first multiple wavelength (per direction), standards-based passive optical network system that is compatible with power-split optical distribution networks. The physical media dependent layer recommendation (ITU-T G.989.2) is the result of over three years of collaborative work by members of the FSAN and ITU-T Study Group 15, Question 2 groups. This two-part paper provides the technical insight and rationales behind the recently approved standard. The first part of the paper focuses on optical link design topics, including the optical distribution network characteristics, wavelength plan, Raman fiber nonlinearity related degradation, and interchannel cross-talk tolerance. It also describes the wavelength-tuning capability of optical network units and its impact on the physical media dependent layer specification.

Demonstration of a 32

A 1300 nm semiconductor optical amplifier has been developed for extended reach GPON applications. The high gain of 29 dB has and enabled a commercial GPON system to operate over 60 km and with 128-way split.

\,\times\,

Semiconductor optical amplifiers are used to simultaneously demonstrate reach and split extension of a commercial GPON system to the 128 ONT and 60km limits permitted in the GPON transport layer specification.

512 Split, 100 km Reach, 2

Results of a field experiment with a prototype managed GPON reach extender for underground deployment are described. The reach extender has 1+1 protection switching to geographically diverse OLTs.