By aligning it with the Phare du Portzic, it shows the safe route to follow for ships to enter the roadstead.

[1] It also has a red signal that indicates a dangerous sector around the plateau of les Fillettes (literally "the girls"), one of the submerged rocks in the Goulet de Brest — sailors remember this by using the mnemonic "Le Minou rougit quand il couvre les Fillettes" ("the Minou blushes when he covers the girls").

As part of the massive fortification campaign of France under the direction of the Marquis de Vauban, construction on the Fort du Petit Minou bastion was finished in 1697.

Two hundred and forty cannons and a formidable moat helped protect a waterway leading to the military port town of Brest, on France's northwest coast.

The waters offshore are notoriously treacherous, so in 1848, the Phare (lighthouse) du Petit Minou was added in front of the fort to aid navigation through the Goulet de Brest strait.