The standards basis is clear:
- ITU-T G.9804.1 Amendment 3, clause 7.1, requires higher-speed PON systems to support coexistence with GPON or XG(S)-PON and to reuse legacy power splitters.
- Clause 9.3 states that higher-speed PON systems must be able to operate over a legacy ODN.
- Clause 9.4.1 specifies 1:64 as the minimum split-ratio requirement for 50G TDM PON, subject to the overall optical loss budget.
- ITU-T G.9804.3 Amendment 3, clause 6.1 and Table 9-4a, defines the optical path loss classes used to evaluate a branch.
G.9804.3 Amendment 3 defines a nominal 50 Gbit/s downstream line rate and nominal upstream options of 25 Gbit/s and 50 Gbit/s. The former 12.44 Gbit/s upstream option has been deprecated.
Evidence Methodology
| Evidence label | Meaning |
|---|---|
| Standard requirement | A provision or parameter published by ITU-T. |
| Official deployment signal | Information published by a regulator or government body. |
| Operator field test | A result publicly disclosed by a network operator. |
| Supplier-published specification | Product data published by Glory Optical or another supplier. |
| Illustrative calculation | A transparent engineering example, not proprietary field-test data. |
This guide does not claim proprietary 50G PON deployment results or undisclosed customer experience.
50G PON Technology Market: Why ODN Reuse Matters
The commercial value of ODN reuse is not that every passive component can remain unchanged. It is that operators may be able to add higher-capacity services without rebuilding the entire outside plant.
In January 2025, China's Ministry of Industry and Information Technology required pilot networks to support coexistence among GPON, XG(S)-PON and 50G-PON. In April 2026, the ministry reported that 136 ten-gigabit optical-network pilot projects had completed their pilot objectives.
Evidence type: Official deployment signal.
In February 2025, Openreach reported a 50G PON field test over part of its existing Full Fibre network, with 41.9 Gbit/s downstream and 20.6 Gbit/s upstream.
Evidence type: Operator field test.
How to Classify an Existing ODN for 50G PON
An ODN should not be classified as reusable on the basis of fiber age, cable appearance or the current GPON received-power value alone. The decision must cover the complete passive path, including fiber, splitters, connectors, splices, coexistence elements, wavelength-selective filters and closures.
Direct Reuse
The measured optical path fits the applicable loss class, sufficient reserve remains, the wavelength path is compatible and no abnormal reflective or loss event requires repair.
Partial Rehabilitation
The installed fiber remains, but selected connectors, splices, splitters, filters, closures or patching points require remediation and post-repair testing.
Reconstruction
The topology, measured loss, fiber condition or wavelength-selective components cannot satisfy the selected 50G PON design through economical local repair.
Required Output
Record a branch-level decision supported by topology, measured optical path loss, equipment loss class and the actual coexistence-component specification.
| Classification | Existing fiber | Passive-component work | Acceptance basis |
|---|---|---|---|
| Direct reuse | Retained | Routine preparation only | Measured compliant path |
| Partial rehabilitation | Usually retained | Local repair or replacement | Post-repair measurement |
| Reconstruction | Partly or fully replaced | New passive path required | New-build acceptance |
This three-category model is an editorial decision framework derived from published standards. It is not presented as Glory Optical field data.
50G PON Coexistence with GPON and XGS-PON
Migration usually occurs subscriber by subscriber rather than through a simultaneous network-wide cutover. GPON, XGS-PON and 50G PON may therefore need to operate over the same ODN.
The current ITU-T G.9805 Amendment 2 describes three coexistence architectures in clauses 6.1, 6.2 and 6.3.
| Architecture | How it works | Qualification focus |
|---|---|---|
| External CEx | Combines and separates wavelength groups outside the OLT optical module. | Insertion loss, isolation, rack space and patching. |
| Multi-PON module | Integrates coexistence functionality within the OLT optical module. | Supported generations, OPL class and platform compatibility. |
| M:N splitter | Connects separate OLT systems through different splitter input ports. | Splitter loss, receiver filtering, isolation and additional OLT-side fiber. |
External Coexistence Element
An external CEx consumes part of the optical path loss budget. The proposed device must be evaluated using its specified insertion loss and isolation values rather than a generic planning figure.
Multi-PON Module
G.9805 Amendment 2 adds Class C+ and Class D optical path loss specifications for GPON/XG(S)-PON and GPON/XG(S)-PON/50G-PON multi-PON modules. The supported class still depends on the selected equipment and interface.
Splitter-Based Coexistence
This method depends on sufficient isolation between wavelength bands and appropriate filtering in the OLT receivers. Older receivers may require additional wavelength blocking.
50G PON Optical Power Budget and ITU-T Loss Classes
Optical path loss is the total reduction in optical power across the passive network. G.9804.3 clause 3.1.23 identifies fiber, connectors, splices, splitters, wavelength couplers, attenuators and other passive components as possible contributors.
The final acceptance value should come from calibrated end-to-end measurement. A component-based calculation remains useful during procurement, but it should not replace field verification.
Applicable ITU-T Requirements
| 50G PON architecture | OPL class | Attenuation range |
|---|---|---|
| MPM-based coexistence | N1 | 14-29 dB |
| MPM-based coexistence | C+ | 17-32 dB |
| External CEx or direct ODN connection | N1 | 14-29 dB |
| External CEx or direct ODN connection | N2 | 16-31 dB |
| External CEx or direct ODN connection | E1 | 18-33 dB |
| External CEx or direct ODN connection | E2 | 20-35 dB |
Evidence type: Standard requirement. Source: ITU-T G.9804.3 Amendment 3, Table 9-4a.
Illustrative 1x32 Versus 1x64 Calculation
Glory Optical publishes maximum insertion-loss values of 16.8 dB for 1x32 and 20.5 dB for 1x64 within its PLC splitter product series.
Evidence type: Supplier-published specification.
PLC splitter product-series example. The image is from the linked Glory Optical product page. Port count, connector type and packaging must be selected for the project; the photograph alone does not identify the 1x32 or 1x64 configuration used in the calculation.
The example uses 15 km of fiber at an illustrative 0.35 dB/km, a combined 3.0 dB allowance for connectors, splices and coexistence components, and a separate 3.0 dB engineering reserve. None of these planning allowances is presented as field-test data.
| Calculation item | 1x32 example | 1x64 example |
|---|---|---|
| Published splitter insertion loss | 16.80 dB | 20.50 dB |
| 15 km x 0.35 dB/km | 5.25 dB | 5.25 dB |
| Illustrative combined passive-component allowance | 3.00 dB | 3.00 dB |
| Calculated path subtotal | 25.05 dB | 28.75 dB |
| Illustrative engineering reserve | 3.00 dB | 3.00 dB |
| Planning total | 28.05 dB | 31.75 dB |
How to Interpret the Model
On a purely arithmetic basis, 28.05 dB is 0.95 dB below the 29 dB N1 maximum. The 31.75 dB example is 0.75 dB above the 31 dB N2 maximum and 1.25 dB below the 33 dB E1 maximum.
These comparisons are not compliance determinations. They do not confirm that a specific transceiver pair supports the relevant class, and they do not replace measured optical path loss.
The difference between the two published splitter values is 3.7 dB. At the illustrative 0.35 dB/km attenuation value, this is mathematically equivalent to approximately 10.6 km of fiber attenuation. It is not permission to extend network reach by 10.6 km because reach is also constrained by the interface, dispersion and differential distance.
How to Audit an ODN Before 50G PON Deployment
The audit should establish both the topology and the measured condition of the passive path. Glory Optical's FTTH ODN Deployment Guide provides supporting information on ODN components and installation practices. It is a supplier-authored technical resource rather than an independent standard.
Desktop Review
- Fiber route, type and estimated length;
- Splitter stages and ratios;
- Connector, adapter and splice count;
- Closure and termination-box locations;
- Existing coexistence or RF-video components;
- Current OLT and ONU types;
- Previous received-power records;
- Unresolved repairs or undocumented path changes.
A label such as "1x64 ODN" is not enough. The record should distinguish between a single 1x64 splitter and a cascaded arrangement such as 1x4 followed by 1x16.
Field Verification
- Connector end-face inspection and cleaning;
- Calibrated end-to-end optical-loss measurement;
- OTDR testing where event location is required;
- Review of reflective events;
- Splitter-port comparison;
- Post-repair retesting;
- Calculation of remaining margin after actual coexistence loss is included.
Glory Optical's fusion-splicing guide gives a supplier-published reference range for a good fusion splice. Project acceptance should use the operator's approved limit and measured result.
Required Acceptance Evidence
| Evidence | Purpose |
|---|---|
| Port-to-ONU topology | Confirms the actual passive route. |
| Splitter hierarchy | Identifies single-stage or cascaded splitting. |
| End-to-end loss record | Determines measured OPL. |
| OTDR trace | Locates abnormal loss or reflection. |
| Connector inspection record | Documents cleaning and end-face condition. |
| Coexistence-component datasheet | Confirms insertion loss and isolation. |
| Supported OPL class | Links the ODN result to the proposed equipment. |
| Exception and post-repair records | Documents remediation and retesting. |
| Final branch classification | Records reuse, rehabilitation or reconstruction. |
Passive-Component Requirements for 50G PON Procurement
Passive components should be procured against measurable optical and environmental requirements. A generic "50G-ready" description is not sufficient.
PLC Splitter Qualification
The relevant evidence should include maximum insertion loss, uniformity, return loss, directivity, operating wavelength, fiber type, connector configuration, environmental qualification method and batch traceability.
Glory Optical's PLC splitter range lists 1x2 through 1x64 configurations and publishes references to Telcordia GR-1209-CORE and GR-1221-CORE.
A procurement team should request the actual qualification report, tested configuration, laboratory, report date, lot-level test format and any differences between the tested sample and proposed product.
Closures and Termination Hardware
Where the audit identifies environmental damage, limited splice capacity or poor cable management, localized hardware replacement may be justified. Relevant internal resources include:
Dome Fiber Optic Splice Closure
Use as a candidate replacement where an outdoor closure fails sealing, cable-entry, splice-capacity or fiber-management requirements.
Optical Fiber Termination Box
Use as a candidate replacement where indoor termination, adapter organization or bend control does not meet the project design.
Additional component options include:
These pages provide component options, not evidence that a product is automatically suitable for a 50G PON project. Selection must consider fiber count, cable diameter, connector type, sealing method, environmental rating, bend control and installation location.
Recommended Procurement Clause
The bidder shall classify audited ODN branches as direct reuse, partial rehabilitation or reconstruction. Classification shall be supported by topology records, calibrated optical path loss measurements, coexistence-component specifications and the optical path loss class supported by the proposed OLT and ONU interfaces.
Component-based calculations may be used for planning but shall not replace field acceptance measurements. All assumed connector, splice, splitter and coexistence-element losses shall be identified separately.
Any claim of compliance with Telcordia, IEC or another qualification document shall be supported by a current report identifying the tested product, method, laboratory and result.
For project-specific splitter packaging, connectorization, labeling or documentation, Glory Optical's OEM service can be evaluated during the RFQ stage.
50G PON ODN Reuse FAQ
Q: Can an Existing PLC Splitter Support 50G PON?
A: Potentially. ITU-T G.9804.1 requires support for legacy power-splitting ODNs, but the installed splitter must still meet the project's wavelength, insertion-loss, uniformity and return-loss requirements.
Q: Does 1x64 Automatically Qualify Because ITU-T Requires 1:64 Support?
A: No. G.9804.1 clause 9.4.1 makes 1:64 the minimum split-ratio requirement for 50G TDM PON, but explicitly makes it subject to the overall loss budget.
Q: Does ODN Reuse Mean the Existing ONU Can Be Retained?
A: No. Existing GPON or XGS-PON ONUs can continue operating on their original systems during coexistence. A subscriber receiving 50G PON service requires a compatible 50G PON ONU.
Q: Is an OTDR Trace Enough to Approve ODN Reuse?
A: No. OTDR is useful for locating events and estimating distributed loss. Final acceptance should also include calibrated end-to-end optical-loss measurement and comparison with the supported OPL class.
Q: Can a Supplier Guarantee Zero ODN Changes Before an Audit?
A: A supplier may propose a zero-change design, but the result cannot be confirmed before topology review and field measurement. The accurate procurement position is reuse subject to qualification.
Conclusion
50G PON is designed to operate over legacy power-splitting ODNs and coexist with earlier PON generations. That standards objective makes existing fiber and splitters candidates for reuse, not automatically accepted assets.
A defensible decision requires the measured optical path loss, the supported loss class of the selected equipment and a branch classification of direct reuse, partial rehabilitation or reconstruction. The passive network should be retained wherever those three outputs support reuse, with components replaced only where measurement, coexistence design or environmental condition shows that they cannot meet the project requirements.
