At a glance
Tier-1 uses an optical loss test set (OLTS) to verify end-to-end insertion loss, length and polarity. Tier-2 adds an optical time domain reflectometer (OTDR) to locate and characterize connectors, splices, bends and breaks, including individual event loss and reflectance.
Where are they used?
- Data centers: Certify duplex links and MPO-based multifiber trunks before handover, checking loss and polarity across the required fibers.
- Enterprise and campus networks: Verify backbone cabling between telecommunications rooms or buildings and assess individual connectors and splices.
- Network upgrades: Reassess existing fiber against the intended application’s limits and locate connections requiring attention
Do you need both an OLTS and an OTDR?
Follow the project’s acceptance requirements. An OTDR report does not replace required OLTS results.
The expert distinction: a link can pass its total-loss limit while an individual connector has excessive reflectance. OLTS testing establishes overall loss; OTDR testing helps identify where a problem occurs.
On short data center links, OTDR dead zones matter: closely spaced connections may not be resolved individually. Select equipment and settings suited to the link.
Key takeway
Use Tier-1 for end-to-end acceptance and Tier-2 for additional event-level characterization—not as interchangeable tests.
