# Define the coherent operating envelope.

Editorial revision 2026-11-01 — engineering guidance, not a released model specification.

A distance label is only the beginning of a DCI specification.

## Name the mode and its reference

Keep the exact model, management revision, host electrical application, network frame, FEC and modulation together. A rate label or media code alone does not identify a compatible connection. The WBN reference includes different FEC choices under the same 100G code and different code meanings between 400G and 800G models.

OIF 400ZR distinguishes an amplified, noise-limited DWDM application from an unamplified, loss-limited application. OIF 800ZR addresses single-span amplified DWDM DCI. These application scopes do not establish a WBN model's qualified reach. OIF 400ZR §7 · OIF 800ZR §2 .

Enhanced OpenZR+ and non-MSA modes require explicit matching at the peer. Do not assume they interoperate with the base mode. See the documented WBN mode tables for the source distinctions.

## Describe the line path

Specify the operating frequency and mode channel width separately. A module's 6.25 GHz provisioning grid is not a 6.25 GHz optical channel. Check the complete filter path against the selected signal, including mux/demux and any ROADM passbands.

- Unamplified path: record fiber attenuation, connector/splice losses, passive insertion loss and margin. Check receive power against the selected mode's documented conditions.

- Amplified path: retain span losses, amplifier placement, gain and noise assumptions, launch-power plan, filter penalties and received OSNR with its measurement bandwidth.

- Dispersion: check accumulated CD against the selected default or extended range; retain the corresponding module-power condition. A ps/nm compensation limit is not a guaranteed kilometer reach.

- Receive limits: keep sensitivity, operating overload, total power, monitor range and absolute maximum ratings separate.

## Leave unknown conditions open

The specification reference preserves WBN document values without resolving them by inference. Missing OSNR bandwidth, unspecified per-mode FEC, conflicting temperature limits and ambiguous power additions remain open.

Host acceptance also requires the package and thermal interface, permitted module power, CMIS application support and exact firmware qualification. A supported aggregate traffic rate does not prove that a switch exposes every documented host mapping.

Keep a route conditional until both endpoint configurations and the complete line envelope have evidence. This reference site does not simulate or certify an amplified line design.

In practice / Worked example

## A loss budget is only the first check.

Assume an unamplified 20 km route. These planning values are illustrative, not measurements or WBN specifications.

| Contribution | Calculation |
| Fiber | 20 km × 0.25 dB/km = 5.0 dB |
| Four mated connector pairs | 4 × 0.35 dB = 1.4 dB |
| Splices | 0.6 dB |
| Estimated physical loss | 7.0 dB |
| Engineering allowance | 2.0 dB |
| Planned loss requirement | 9.0 dB |
OIF 400ZR application 0x02 specifies an unamplified budget of 11 dB minus link impairments. A 9 dB planning result alone therefore does not prove operation. Check transmit and receive limits, dispersion, reflections and other impairments for the selected application. Amplified paths additionally require noise and OSNR assessment; amplifier gain cannot simply be subtracted to prove feasibility.

Source: OIF · 400ZR Implementation Agreement ↗ OIF-400ZR-03.0 · 8 October 2024 · §7.2, Table 19 (page 63)

## Before you specify

- Exact host and line mode at both endpoints

- Frequency, signal width and complete filter path

- Launch / receive power, OSNR and dispersion conditions

- Host power, thermal and firmware support

- Unresolved source conflicts and release evidence

## Sources & scope

General engineering guidance. External examples describe their own products and do not establish WBN availability or qualification.

- 400ZR implementation agreement ↗ OIF · OIF-400ZR-03.0 · 8 Oct 2024

- 800ZR implementation agreement ↗ OIF · OIF-800ZR-01.0 · 8 Oct 2024

- WBN coherent document reference Six mapped WBN Rev 1.0 documents; unreleased values and gaps retained per model

Source: OIF 400ZR §7 — https://www.oiforum.com/wp-content/uploads/OIF-400ZR-03.0.1.pdf
Source: OIF 800ZR §2 — https://www.oiforum.com/wp-content/uploads/OIF-800ZR-01.0.pdf
Source: OIF · 400ZR Implementation Agreement ↗ — https://www.oiforum.com/wp-content/uploads/OIF-400ZR-03.0.1.pdf
Source: 400ZR implementation agreement ↗ — https://www.oiforum.com/wp-content/uploads/OIF-400ZR-03.0.1.pdf
Source: 800ZR implementation agreement ↗ — https://www.oiforum.com/wp-content/uploads/OIF-800ZR-01.0.pdf