Hello, everyone!
Today, I would like to share with you an article on FTTH-PON networks – Overlay operation.
FTTH-PON Upgrade When capacity runs out or gigabit services aren't supported, phased transition toward a new standard with "overlay" functioning of OLTs and ONTs from two generations along the same ODN might well be necessary.
Acquisitions of new hardware are staggered over time, primarily to satisfy requests by prospective consumers or to provide new services, rather than replacing old hardware at clients who refuse to upgrade.
With the exception of ancient GPON devices, overlay operation is maintained by the assignment of different wavelength bands, as seen in Table 1, with each of the three system generations:
(1) GPON,
(2) NG–PON2 (view below Table 2).
(3) 10G EPON, XG–PON, and XGS–PON,
(i) 1260–1360 nm at first.
(ii) G.989 of the International
Telecommunication Union. 2 sets of bands are also narrower: 1528–1540 nm
and 1532–1540 nm.
Table 1 shows the wavelength bands for FTTH-PON systems (values in [nm]).
Remarked: (i) XG-PON too is regarded as NG-PON1;
(ii) ITU-T Recommendations are provided in series, e.g., G.987, G.987.1, and so forth;
(iii) all IEEE standards, which were once distinguishable, have become part of 802.3;
(iv) date of standardization refers to first document;
(v) GPON capacity data refer to dominant "recommended method" variant.
Table 2 describes the correlation of FTTH-PON systems that are currently in use or are scheduled for implementation.
The 1550–1560 nm wavelength range is designated for analog television transmission. At the OLT and ONT, WDM multiplexers and wavelength blocking filters should be added, resulting in a cumulative loss of up to 2 dB.
The focus of ITU-development T's work has turned to expanding OLT capacities.
Nevertheless, increasing the bit rate at a single-carrier wavelength to 40 or 100 Gb/s for transmitting across a conventional single-mode fiber with a range of 20–40 km necessitates multilayered coherent modulation and identification, as well as digital fiber dispersion compensation.
Following 2006, such technology was effectively adopted in core and metropolitan networks, but it is too complex and expensive in access networks.
You are welcome to leave a message and exchange in the comment area. Thank you!
