2.Passive optical network technologies The Passive Optical Network (PON)is a network,which carries data in the optical domain between the OLT and the ONU or ONT and the transport path of the optical signal is passive.This implies that the optical network devices (between the transmitter and receiver)are non-powered,i.e.no electrical devices are used.The basic PON principle is summed up in [1]by the following phrase: "The basic principle of PON is to share the central Optical Line Termination (OLT)and the feeder fibre over as many Optical Network Units (ONUs)as is practical given cost effective optics." 2.1 Standard development The first PON activity was in the 1980s when many of the largest carriers around the world worked together to introduce optical access solutions into their networks.However,these remained only as trial applications due to the high cost and relatively low demand at the time.The Internet became common in the 1990s,which brought out the need for efficient broadband access.A group of seven major network operators established the Full Service Access Networks (FSAN)consortium in 1995 to derive a common set of requirements for optical access systems [2].In 1998,this resulted in ITU-T Recommendation G.902 and, in 1999,ITU-T adopted the new specifications as the 155 Mbit/s PON system (ITU-T Recommendation G.983 series).This was named as the Broadband PON (B-PON)or more commonly as Asynchronous Transfer Mode (ATM)based PON (A-PON or ATM-PON)[3]. While FSAN and ITU-T were actively improving B-PON,Ethernet was gaining more and more popularity.Institute of Electrical and Electronics Engineers (IEEE)established the Ethernet in the First Mile(EFM)study group,which later developed to IEEE 802.3ah task force.This task force had an E-PON sub-task force,which focused on standardising the Ethernet based 1 Gbit/s symmetrical PON system.The work has been finalised and the first version of the standard An ONT is an ONU used for FTTH that includes the User Port function.[G.984.1] 20￾       !"#$!%&'()$*+!%&'(,%""''-!+! & !"#-&.+/!%+!0+-!$1&'$2+-!!'+ &'! ! &3!& !"#4+# 5. #!!!& !"#+!%&'(-" )/!%+!!'+.!!'+-'"'*'+&+6 &%'-,55+&#"!'"#-" '7-5/"$ '+" #7..-7 +829/:!3&##&%+4 '; <=>?@ABCDEFCGDCEH?IJKLMCBNIB>AF?N>?D?GNFAHLENCDAHOCG?=?FPCGANCIG QLO=RAGSN>?J??S?FJC@F?IT?FABPAGULENCDAHM?NVIFWXGCNBQLMXBRABCB EFADNCDAHYCT?GDIBN?JJ?DNCT?IENCDBZ< [\]]]  ^ 3'!$"!!:%+!2_`%+.+:&3!#'4!"''''&7+- !%&'#-%&'(-!&4!'!&+!'&-7"& !"#""&#7!&++!&!' +!%&'(5a&%',!'.+-&+#:!'# #"!&+-7!&!4"&! +-'#!#:#&%-.+-!!!.5b+!'+!/"."&..&++! 2__,%"/'&74!&7!!+-3&'33"+!/'&-/+-""5c4'&7 &3 +.d&'+!%&'(& '!&'!/#-!e7##f'"c""$!%&'( )efc$*"&+&'!7.+2__g!&-'"&..&+!&3'h7'.+!3&'& !"# "":!.8￾95b+2__`,!'7#!-+b16i"&..+-!&+j5_￾+-, +2___,b16-& !-!+% "3"!&+!2ggk/!l$:!. )b16i"&..+-!&+j5_`m'*5%+.-!n'&-/+-$ )n6$*&'.&'"&..&+#:c:+"'&+&7'+3'k&-)ck*/- $)c6$&'ck6$*8m95 o#efc$+-b16%'"!#:. '&+4n6$,p!'+!%4++4 .&'+-.&' & 7#'!:5b+!!7!&3p#"!'"#+-p#"!'&+"p+4+' )bppp*!/#-!p!'+!+!e'!k#)pek*!7-:4'&7 ,%"#!' -#& -!&bppp`￾5m!(3&'"5!(3&'"-+p6$7/6!( 3&'",%"3&"7-&+!+-'-+4!p!'+!/-2j/!l:..!'"# $:!.5%&'(/+3+#-+-!3'!'&+&3!!+-'- 2c+$+$17-3&'ea!!+"#7-!1'&'!37+"!&+58j5_`q529