diff --git a/sql/111-ieee-msa-wavelength-lookup.sql b/sql/111-ieee-msa-wavelength-lookup.sql
index b081730..a9de3bc 100644
--- a/sql/111-ieee-msa-wavelength-lookup.sql
+++ b/sql/111-ieee-msa-wavelength-lookup.sql
@@ -9,7 +9,7 @@ CREATE TABLE IF NOT EXISTS ieee_wavelength_lookup (
   fiber_type      TEXT    NOT NULL,   -- 'SMF', 'MMF', 'DAC', 'AOC'
   reach_min_m     INTEGER NOT NULL,
   reach_max_m     INTEGER NOT NULL,
-  wavelength_tx_nm INTEGER NOT NULL,
+  wavelength_tx_nm INTEGER,           -- NULL for Copper/RJ45 (no optical wavelength)
   wavelength_rx_nm INTEGER,           -- NULL = gleich wie TX (kein BiDi)
   connector_type  TEXT    NOT NULL,
   ieee_standard   TEXT,               -- z.B. '802.3ae', 'SFF-8431'