TP-Link releases "Tapo L900-10", a 10m version of a smart Wi-Fi tape light that can be cut to any length.Since NTT Higashi started providing the Internet connection service "B FLET'S" using optical fiber in 2001, the speed has continued to increase from the initial 10M / 100Mbps, and in 2015 Sony Network Communications Co., Ltd. With the new plan of "NURO Hikari" that we have started to provide, we have finally reached 10 Gbps.In 2017, the target area of ​​"NURO Hikari 10G" expanded, and 10Gbps Internet connection service became available in many areas.This time, we will explain the access line standard "GE-PON" that uses 1 Gbps optical fiber standardized as "IEEE 802.3ah".(Editorial department)The "E-PON" explained last time did not become a standard after all.As explained, in "IEEE 802.3ah", 100Mbps was skipped and 1Gbps was targeted.The final standard was "1000BASE-PX", although this name is not often used.There are exactly four types of this 1000BASE-PX.In short, different names are assigned for distance (10km or 20km) and up / down (OLT → ONU / ONU → OLT), but the basics are the same.Strictly speaking, in IEEE 802.3ah, "1000BASE-LX10" and "1000BASE-LX10" using 2-core optical fiber, "100BASE-BX10" and "1000BASE-BX10" using 1-core optical fiber, Furthermore, up to "10BASE-TS" (10Mbps / 750m) and "2BASE-TL" (2Mbps / 2700m) using coaxial cables are defined as "PMD (Physical Medium Dependent)" of PON.However, other than 1000BASE-PX, it is rarely used, and I investigated why 100 / 1000BASE-LX and 100 / 1000BASE-BX were adopted as PMD in the first place, but the reason was not clear.For this reason, I would like to omit it here.Hereinafter, the word GE-PON will be described as referring to 1000BASE-PX10 / 20 in IEEE 802.3ah.Since GE-PON uses Ethernet frames as they are, the frame size is variable.The difference is the preamplifier part of the header part, and 2 bytes of the 8-byte preamplifier are assigned to "LLID (Logical Link ID)".Even with GE-PON, the principle of transmission and reception is the same as the "B-PON" explained last time, and in the OLT → ONU direction, all ONUs receive all frames sent by OLT.For this reason, the ONU looks at the LLID, discards frames that are not addressed to it, and receives only frames that are addressed to it.In GE-PON, two new technologies have been added from B-PON.One of them is "P2MP Discovery".This is a mechanism in which when a new ONU is connected to PON, OLT automatically discovers the ONU, adds an LLID, and establishes a link.At this time, OLT measured the "RTT (Round Trip Time)" with the ONU to correct the timing, and was also equipped with a mechanism to synchronize the time.The other is upstream bandwidth control (that is, ONU → OLT direction).Basically, in ONU → OLT communication, in order to prevent "signal collision" in which signals transmitted by multiple ONUs collide with each other at the tip of the optical splitter, a control frame called "GATE" is used in advance. The OLT notifies each ONU of the allowable transmission start time and the amount of transmission data.By observing the timing notified by GATE and the amount of transmitted data, each ONU will be able to perform all ONU → OLT communication without data collision.By the way, the problem here is how to share the bandwidth among multiple ONUs.In B-PON, the function of "DBA (Dynamic Bandwidth Assignment)" was added in "G.983.4" established in December 2001, but DBA was also adopted in GE-PON.This function is performed using the "REPORT" frame, which is used as a pair with the GATE frame.When the start time and the amount of data that can be transferred are assigned to each ONU in the GATE frame, each ONU starts sending data according to the start time.When the data transmission is completed, the ONU finally sends a control frame called REPORT to the OLT.This is a notification of the completion of transmission, but at the same time, it also notifies the OLT of "how much untransmitted data the ONU has when the transmission is completed".Therefore, on the OLT side, it is possible to determine how much untransmitted data each ONU has after a series of operations for allocating the transmission band to the ONUs.Therefore, in the next sequence, the PON bandwidth is allocated by allocating a large amount of transfer to an ONU with a large amount of untransmitted data, a small amount to an ONU with a small amount of untransmitted data, and no transfer to an ONU with no untransmitted data. It is a mechanism that can be used effectively.Actually, the algorithm itself on the OLT side is not specified by IEEE 802.3ah.For this reason, 1 Gbps may be mechanically divided evenly over a maximum of 32 ONUs, and a kind of QoS-like operation such as allocating a large amount as an option to the ONUs of users' homes with a premier contract is also possible. be.In the case of NTT, NTT East started providing services using GE-PON in 2004 as "B FLET'S Hyper Family Type" and NTT West as "FLET'S Hikari Premium" in 2005.In addition, Yahoo! BB also started providing connection services using GE-PON in October 2004.In the case of au, the connection form at the time of the original "TEPCO Hikari" is not clear, but when au integrated this TEPCO Hikari as "Hikari one" in 2006, it announced that it would clearly use GE-PON. Has been done.This time, I explained the access line standard "GE-PON" using 1 Gbps optical fiber standardized as IEEE 802.3ah.Next time, I will explain the access line standard "G-PON" that uses another optical fiber that supports 1 Gbps.Free technical writer.We have a wide range of fields of expertise, from CPUs, memories and chipsets to communication-related, OS, databases, and medical-related fields.The homepage is http://www.yusuke-ohara.com/"B-PON" with a maximum of 622 Mbps adopted for "B FLET'S" (100 Mbps) of NTT East and WestCopyright © 2018 Impress Corporation. All rights reserved.