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INSTITUTION PROFILE / OPTICAL COMMUNICATIONS & PHOTONICS

ITU-T (Study Group 15)
The UN forum that writes the international Recommendations for optical fibre and optical transport networks

ITU-T is the Telecommunication Standardization Sector of the International Telecommunication Union (ITU), a specialised agency of the United Nations. Optical communications fall to Study Group 15 (SG15), which writes Recommendations on the characteristics of optical fibre and cable (such as G.652), optical transport networks (OTN, G.709), optical interfaces for wavelength division multiplexing (G.698.2) and optical access (PON). Its influence is strongest not inside the data centre but over optical fibre itself and the optical transport networks that connect carriers and data centres. This profile looks at one question only: how much influence ITU-T actually has over optical communications and photonics.

Sources: the ITU and ITU-T websites (organisational overview, status of Recommendations, approval procedures), SG15's pages (mandate, executive summary of the July 2026 meeting) and ITU-T Recommendation pages, used as primary information. Last updated September 2026.

What this article covers

ITU-T in 30 seconds
What kind of body it is: the four types of influence
What it does in optical communications and photonics
How far its influence reaches (powers and geography)
The countries and organisations involved
Outlook
Glossary, references and claim-to-source audit

1. ITU-T in 30 seconds

FULL NAMEInternational Telecommunication Union Telecommunication Standardization SectorKnown as ITU-T. Optical communications are handled by Study Group 15 (SG15)

COUNTRYInternational organisation (UN specialised agency)Headquarters in Geneva, Switzerland

TYPE OF BODYStandards arm of an intergovernmental organisationFounded in 1865, ITU is the oldest agency in the UN system

MEMBERSHIP194 member states plus more than 1,000 companies, universities and othersMembership of ITU as a whole. Companies take part as sector members

SIZE (SG15 MEETING)377 people from 40 countriesAttendance at the July 2026 meeting in Montreal. More than 500 registered

SG15 MANDATEOptical transport, access networks, optical fibre and cableITU-T's lead study group on optical technology

ROLE IN PHOTONICSWriting international standards (Recommendations)G.652 optical fibre, G.709 OTN, G.698.2 DWDM, 50G-PON and more

REACHMember states and the companies that adopt its RecommendationsRecommendations are voluntary until written into national law

The one thing to grasp first

ITU-T Recommendations are voluntary standards until a country writes them into its national law. ITU-T itself explains that Recommendations are not mandatory unless adopted as part of national law, but that compliance is nonetheless high because they are internationally applicable and of high quality Sourced. It is the only intergovernmental organisation among the eight institutions in this series, with 194 member states, yet like OIF and IEEE 802.3 it has no power to enforce its standards. Its influence comes from the fact that its definitions of optical fibre characteristics and optical transport network specifications are used as a shared international reference by carriers and manufacturers in every country.

2. What kind of body it is: the four types of influence

Unlike the companies in this series, the institutions that appear in our optical communications and photonics coverage do not sell optical components. What separates them is the route by which they influence the industry, and that gives four types.

Fig. 1 Four types of institution involved in optical communications and photonics, and where ITU-T sits. The classification is our own; the examples are the eight institutions covered in this series and the government agencies that fund them Our calculation. MIC is Japan's Ministry of Internal Affairs and Communications and DoD the U.S. Department of Defense. ITU-T is a sector of the ITU, a UN specialised agency, and the only intergovernmental organisation among the eight. We place it under Standards rather than regulation because what it produces is Recommendations.

3. What it does in optical communications and photonics

SG15 is responsible for standards on the infrastructure, systems and equipment of optical transport networks, access networks, home networks and power utility networks, and on optical fibre and cable. It has been designated ITU-T's lead study group on optical technology Sourced. Its main Recommendations, and the developments at its July 2026 meeting in Montreal, are as follows.

Area	Key Recommendations (current edition)	What they cover	Developments at the July 2026 meeting
Optical fibre and cable	G.652 (August 2024 edition)	Characteristics of single-mode optical fibre and cable	Geometric characteristics of weakly coupled multicore fibre added to the scope of the G.650.1 revision. A new technical report on hollow-core fibre started
Optical interfaces for WDM	G.698.2 (November 2018 edition)	Single-channel optical interfaces for amplified multichannel DWDM systems	Work continuing to add 800G DWDM to the revised G.698.2, with beyond-1-terabit (B1T) interfaces also being added in the revision
Optical transport networks (OTN)	G.709/Y.1331 (June 2020 edition plus amendments)	Interfaces for the optical transport network	A 1.6Tb/s long-haul interface specified in G.709.6 (FlexO). It uses the same optical interface as OIF's 1600ZR+, so the same optical modules can be used for both
Optical access (PON)	G.9804.3 (September 2021 edition plus amendments)	Physical layer for 50G-PON	Work on very high speed PON (VHSP) continuing
Incorporating Ethernet	G.8020.3	Covers Ethernet within ITU-T's transport network Recommendations	The third edition incorporates IEEE Std 802.3-2022 and its amendments by reference. A liaison was sent to IEEE 802.3

Across the whole meeting, SG15 received 438 contributions and consented 33 texts, including 2 new and 12 revised Recommendations. It also held three workshops on the impact of AI, one of them jointly with IEEE 802 Sourced.

A materials engineer's view: ITU-T is where the definition of optical fibre changes

Optical transceivers inside the data centre follow IEEE 802.3 and OIF specifications, but the characteristics of the optical fibre that carries their light are defined in ITU-T Recommendations such as G.652. At the July 2026 meeting, work got under way on measurement methods for multicore fibre (the G.650.1 revision) and on a technical report on hollow-core fibre. For companies dealing in optical fibre, cable jacketing materials and connecting components, whether a new type of fibre is defined in a Recommendation is what decides whether it makes it into international procurement requirements (this is our own view).

4. How far its influence reaches (powers and geography)

Aspect	What ITU-T has	What it does not have
Powers	The power to approve Recommendations agreed in its study groups and publish them as international standards	Power to enforce Recommendations (voluntary until written into national law), or to fund research
Geography	International. A UN specialised agency with 194 member states, headquartered in Geneva	Power to decide how each country treats a Recommendation at home
Approval procedure	Most Recommendations go through the Alternative Approval Process (AAP), a four-week comment period in which member states and sector members take part on an equal footing. Those with regulatory implications use the Traditional Approval Process (TAP)	Voting by individuals (unlike IEEE 802.3)
Membership	Member states, plus sector members such as companies, universities and international organisations (more than 1,000 across ITU)	Power to require non-member companies to take part or to adopt its Recommendations
Relations with other bodies	Joint workshops with IEEE 802; liaisons to IEEE 802.1, IEEE 802.3 and IEC TC86 SC86A; a common optical interface with OIF's 1600ZR+	Power to change IEEE or OIF standards directly

A note on reading the numbers

The figures of 194 countries and more than 1,000 members refer to ITU as a whole, not to the number of countries or companies taking part in SG15. A better guide to SG15's size is the 377 people from 40 countries who attended its July 2026 meeting. The number of countries that have written individual Recommendations into national law or into carriers' procurement specifications is not given in the primary information checked for this article Not yet confirmed.

5. The countries and organisations involved

Fig. 2 How a Recommendation is made in ITU-T SG15, and the organisations it works with. Sources: ITU-T's approval procedures page, ITU-T Recommendation pages, SG15's pages and the executive summary of its July 2026 meeting, and OIF's liaisons page Sourced.

SG15's meeting summary mentions, among other things, that China Unicom will host an interim meeting in Chengdu, but the primary information checked for this article does not reveal any relationship with the companies profiled in this series. We therefore do not name individual companies here.

6. Outlook

What the evidence suggests	Primary information it rests on	Category
International standards for 1.6T and beyond 1 terabit (B1T) will also be in place for carriers' optical transport networks, and more optical modules will be shared between data centre interconnect and carrier networks	G.709.6 specifies a 1.6Tb/s long-haul interface with an optical interface in common with OIF's 1600ZR+. A revision adding 800G DWDM and B1T to G.698.2 is in progress	Inference
Multicore fibre and hollow-core fibre will gradually come within the scope of Recommendations	Weakly coupled multicore fibre added to the scope of the G.650.1 revision; a technical report on hollow-core fibre started; a liaison sent to IEC TC86 SC86A	Inference
Optical networks for AI data centres will become a new topic of study for SG15	Three AI-themed workshops held in July 2026, and a technical report, TR.ION-aiDC (the "aiDC" in its name standing for AI data centres), being developed under the ION-2030 framework	Inference

7. Glossary

Recommendation: The formal name for an ITU-T international standard. Voluntary until written into a country's national law.

SG15: ITU-T Study Group 15, responsible for optical transport networks, access networks, and optical fibre and cable.

OTN / FlexO: OTN is the framework for carriers' optical transport networks. FlexO is a method for flexibly bonding high-speed interfaces, defined in the G.709.x series of Recommendations.

AAP: Alternative Approval Process: a fast-track procedure in which a text is approved if no comments are received during a four-week comment period after consent.

Sector Member: A company, university or organisation that takes part in ITU's work, joining member states in developing Recommendations.

8. References

ITU About ITU: UN specialised agency, 194 member states and more than 1,000 companies, universities and international organisations, headquarters in Geneva, founded in 1865. https://www.itu.int/en/about/Pages/default.aspx
ITU-T ITU-T in brief: study groups and Recommendations, and the role of the TSB. https://www.itu.int/en/ITU-T/about/Pages/default.aspx
ITU-T ITU-T Recommendations: Recommendations are not mandatory until adopted in national law, but compliance is high. https://www.itu.int/en/ITU-T/publications/pages/recs.aspx
ITU-T Standards approval: AAP and TAP, the four-week Last Call, and equal opportunity for member states and sector members. https://www.itu.int/en/ITU-T/about/Pages/approval.aspx
ITU-T SG15 Mandate and lead roles: SG15's mandate and its role as lead study group on optical technology. https://www.itu.int/en/ITU-T/studygroups/2025-2028/15/Pages/mandate.aspx
ITU-T SG15 Executive Summary (July 2026, Montreal): attendance, contributions and texts consented; developments on G.650.1, G.698.2, G.709.6 and G.8020.3; liaisons to IEEE 802 and IEC TC86 SC86A. https://www.itu.int/en/ITU-T/studygroups/2025-2028/15/Pages/exec_sum_2026-07.aspx
ITU-T SG15 home page: the 10th joint workshop with IEEE 802, and sessions and exhibits at OFC 2026 and ECOC 2026. https://www.itu.int/en/ITU-T/studygroups/2025-2028/15/Pages/default.aspx
ITU-T Recommendation G.652 (current edition, August 2024). https://www.itu.int/rec/T-REC-G.652/en
ITU-T Recommendation G.709/Y.1331 (current edition, June 2020, with amendments and corrigenda). https://www.itu.int/rec/T-REC-G.709/en
ITU-T Recommendation G.698.2 (current edition, November 2018). https://www.itu.int/rec/T-REC-G.698.2/en
ITU-T Recommendation G.9804.3 (50G-PON physical layer; current edition, September 2021, with amendments). https://www.itu.int/rec/T-REC-G.9804.3/en
OIF Liaisons: OIF's liaison to ITU SG15. https://www.oiforum.com/technical-work/liaisons/

9. Claim-to-source audit

Claim in the article	Category	Source
UN specialised agency, 194 countries and more than 1,000 members, headquarters in Geneva, founded in 1865	Sourced	Reference 1 https://www.itu.int/en/about/Pages/default.aspx
Study groups write international standards (Recommendations)	Sourced	Reference 2 https://www.itu.int/en/ITU-T/about/Pages/default.aspx
Recommendations voluntary until adopted in national law; compliance is high	Sourced	Reference 3 https://www.itu.int/en/ITU-T/publications/pages/recs.aspx
AAP and TAP; four-week comment period	Sourced	Reference 4 https://www.itu.int/en/ITU-T/about/Pages/approval.aspx
SG15's mandate; lead study group on optical technology	Sourced	Reference 5 https://www.itu.int/en/ITU-T/studygroups/2025-2028/15/Pages/mandate.aspx
July 2026 meeting: 377 attendees from 40 countries, 438 contributions, 33 texts consented, developments on each Recommendation, liaisons	Sourced	Reference 6 https://www.itu.int/en/ITU-T/studygroups/2025-2028/15/Pages/exec_sum_2026-07.aspx
10th joint workshop with IEEE 802; activities at OFC and ECOC	Sourced	Reference 7 https://www.itu.int/en/ITU-T/studygroups/2025-2028/15/Pages/default.aspx
Current edition and title of G.652	Sourced	Reference 8 https://www.itu.int/rec/T-REC-G.652/en
Current edition and title of G.709/Y.1331	Sourced	Reference 9 https://www.itu.int/rec/T-REC-G.709/en
Current edition and title of G.698.2	Sourced	Reference 10 https://www.itu.int/rec/T-REC-G.698.2/en
Current edition and title of G.9804.3	Sourced	Reference 11 https://www.itu.int/rec/T-REC-G.9804.3/en
OIF's liaison to SG15	Sourced	Reference 12 https://www.oiforum.com/technical-work/liaisons/
The four types of institution; the view that the definition of optical fibre decides procurement requirements	Our calculation	Our own analysis
Number of countries that have written each Recommendation into national law or procurement specifications	Not yet confirmed	Not stated in references 1 to 11; this article does not estimate it
The three points in the outlook (section 6)	Inference	This article's reading of references 6 and 7

Last updated 26 September 2026 / Troy Technical
All statements come from the ITU and ITU-T websites (including SG15's meeting summaries and Recommendation pages) and from OIF's website. Items marked "Inference" are this article's reading of the primary information, not statements by ITU.