Dear Xuan,
There will be SSO and the browser will not pop-up for authentication if the service providers, requested by the user, will be trusted by the SAP SAML IDP configured for Fiori. A new passcode will not be necessary for the SAML IDP to issue a SAML assertion for another service provider (trusted by the IDP) when the user already has a active session on the IDP.
So, it is similar to the "desktop world".
Regards,
Donka Dimitrova